1 Introduction
2 Literature review
3 Methodology
- Alliance-based connection: The connection is between flights operated by carriers belonging to the same alliance;
- On-line connection: The connection is between flights operated by the same carrier, which is unallied but still a traditional carrier. An example of on-line connections is those involving the independent Gulf airlines such as Emirates and Etihad;
- Self-connection: The connection is not classified in the two previous groups. It involves a transfer between independently ticked flights operated by unrelated carriers, belonging to either different alliances, independent, or low-cost carriers.
- The time between the incoming and outgoing flights must be higher than a minimum connecting time (MCT). Table 1 reports the different assumed MCTs for the different connections and different geographical regions.
- The routing factor of the one-stop itinerary starting from the origin of the incoming flight, passing through the considered airport, and arriving at the destination of the outgoing flight must be 1.4 or less for intra-European connections, and 1.2 or less for intercontinental connections [8]. The detour necessary to complete the trip must be at most 40% of the direct distance between the origin and destination in the case of EU connections, and 20% in the case of intercontinental connections. This condition aims to exclude some low-quality O-D connections that are not attractive for passengers due to long detours, such as going from Rome to Barcelona via London.
- The quickest travel time is implemented following the minimum travel time approach ([26]; for a detailed explanation see [25], pp. 56), including both flight times and waiting times spent in the intermediate airport. It is computed for all O-D pairs that met the abovementioned two conditions. As in Redondi et al. [27], the last condition for a connection to be considered requires that its travel time does not exceed that of the quickest alternative by more than 40% in the case of EU connections and 20% in the case of intercontinental connections. This last condition discriminates the quality of connections by considering only those with the highest probability of being considered by passengers. It generally excludes connections with long waiting times spent in intermediate airports.
Minimum connecting times (minutes) | Intra-EU connections | Intercontinental connections |
---|---|---|
Alliance-based and on-line connections | 45 | 60 |
Self-connections | 90 | 120 |
4 Empirical analysis
4.1 Connection performances
Quickest 2-step connections by type | Intra-EU | Extra-EU | ||
---|---|---|---|---|
No. | % | No. | % | |
No. of 2-step indirect connections | 32,673 | 10,308 | ||
% of 2-step viable connections | 67.1% | 49.9% | ||
Total no. of viable 2-step connections | 21,914 | 100% | 5142 | 100% |
Alliances | ||||
OneWorld | 2411 | 11.0% | 900 | 17.5% |
Sky Team | 1994 | 9.1% | 1136 | 22.1% |
Star Alliance | 3046 | 13.9% | 1193 | 23.2% |
Online | 789 | 3.6% | 77 | 1.5% |
Self-connection | 13,893 | 63.4% | 1923 | 37.4% |
Viable 2-step connections by type | Intra-EU | Extra-EU | ||||
---|---|---|---|---|---|---|
Avg. time index | Conn. time | Rout. Fact. | Avg. time index | Conn. time | Rout. Fact. | |
Alliances | ||||||
OneWorld | 112.8% | 92.9 | 1.11 | 107.2% | 129.1 | 1.07 |
Sky Team | 112.9% | 89.0 | 1.11 | 106.6% | 123.0 | 1.07 |
Star Alliance | 114.6% | 87.3 | 1.11 | 106.8% | 121.4 | 1.06 |
Online | 108.4% | 114.0 | 1.10 | 106.2% | 141.3 | 1.03 |
Self-connect | 115.8% | 139.6 | 1.10 | 109.2% | 171.2 | 1.06 |
Total no. of viable 2-step connections | 114.7% | 116.2 | 1.11 | 107.7% | 140.8 | 1.06 |
4.2 Frequencies and return trip availability
OneWorld | SkyTeam | Star Alliance | Online | Self connect | Total | % self connect | ||
---|---|---|---|---|---|---|---|---|
European Connections | No. viable connect. | 27,586 | 41,293 | 52,995 | 4593 | 142,208 | 268,675 | 52.9% |
No. O-D pairs | 3367 | 2799 | 3802 | 969 | 18,515 | 29,452 | 62.9% | |
Average freq. | 8.2 | 14.8 | 13.9 | 4.7 | 7.7 | 9.1 | 84.6% | |
Extra-EU Connections | No. viable connect. | 17,139 | 25,368 | 26,790 | 607 | 38,610 | 108,514 | 35.6% |
No. O-D pairs | 1591 | 1900 | 1809 | 138 | 3854 | 9292 | 41.5% | |
Average freq. | 10.8 | 13.4 | 14.8 | 4.4 | 10.0 | 11.7 | 85.5% | |
Total Connections | No. viable connect. | 44,725 | 66,661 | 79,785 | 5200 | 180,818 | 377,189 | 47.9% |
No. O-D pairs | 4958 | 4699 | 5611 | 1107 | 22,369 | 38,744 | 57.7% | |
Average freq. | 9.0 | 14.2 | 14.2 | 4.7 | 8.1 | 9.7 | 83.5% |
- Scenario I: This scenario considers the daily return trip in which passengers spend at least 4 h at their destination and return to their origin airport. This is a typical scenario for business passengers. Interestingly, by employing self-connections, the likelihood of being able to make a return trip of this kind is only 9.2% given the total number of offered O-D pairs, as shown in Table 4. The Skyteam and Star alliances have much higher daily return trip ratios, 48.1% and 35.1%, respectively. On average, when the daily round trip is feasible, there are 1.18 return options.
- Scenario II: A daily round trip can be made in a city pair. This scenario is therefore less demanding than the previous one as it allows passengers to make the return trip by employing other O-D pairs, as long as they connect to the same cities. For example, a passenger may depart from London Gatwick to reach Catania airport via Rome Fiumicino. The return trip may be from Catania airport to London Stansted via Bergamo airport. However, even in this case, the number of city pairs that can be connected does not increase significantly with respect to the previous scenario. The return trip ratio of self-connections increases to 10.3%. However, the same figure for SkyTeam and Star alliances is about four times as much, 48.5% and 35.6%, respectively.
- Scenario III: The return trip has to be made during the week and passengers spend at least 24 h at their destination. This scenario better represents the behavior of leisure passengers as well as that of business passengers. In this case, by self-connecting, passengers can make a round trip in 65.8% of all viable O-D pairs. The difference between self-connection and other kinds of connections is relatively low in this scenario. However, when looking at the number of return options, the lower quality of self-connections becomes evident again. Self-connecting passengers have an average of 3.7 return options during the week, while Skyteam offers 7.87 options and Star offers 12.6 options.
- Scenario IV: Passengers are still allowed at least 24 h at a destination, but the one-way and return trips must be operated by the same carriers. This is a more demanding scenario than the previous one and measures the robustness of the round trip with respect to the choice of the carrier. Given the fact that even LCCs have recently begun to promote frequent flyer programs, in which they offer more booking flexibility and higher quality standards, business passengers may be interested in return trips operated by the same carriers. The performances of the different kinds of connections are similar to those related to the previous scenario; self-connection passengers have only 3.82 return options available. The exception to this is the Star alliance, whose return travel options are 8.65 on average, almost double that of the other groups.
OneWorld | SkyTeam | Star Alliance | Online | Self connect | Total | ||
---|---|---|---|---|---|---|---|
Scenario 1 Daily return trip (al least 4 h at destination) | O-D pairs | 603 | 1347 | 1335 | 112 | 1698 | 5095 |
% O-D linked | 17.9% | 48.1% | 35.1% | 11.6% | 9.2% | 17.3% | |
No. return options | 1.18 | 0.93 | 1.34 | 0.80 | 1.09 | 1.18 | |
Scenario 2 Daily return trip at city-pairs (al least 4 hours at destination) | City pairs | 624 | 1354 | 1352 | 113 | 1913 | 5356 |
% City linked | 18.5% | 48.4% | 35.6% | 11.7% | 10.3% | 18.2% | |
No. return options | 1.25 | 1.11 | 1.37 | 0.84 | 1.08 | 1.25 | |
Scenario 3 Return trip (al least 24 h at destination) | O-D pairs | 2496 | 2531 | 3018 | 587 | 12,184 | 20,816 |
% O-D linked | 74.1% | 90.4% | 79.4% | 60.6% | 65.8% | 70.7% | |
No. return options | 8.87 | 7.87 | 12.60 | 6.47 | 3.70 | 8.87 | |
Scenario 4 Return trip (at least 24 h at destination) – same carriers | O-D pairs | 2427 | 2519 | 2982 | 568 | 10,096 | 18,592 |
% O-D linked | 72.1% | 90.0% | 78.4% | 58.6% | 54.5% | 63.1% | |
No. return options | 5.13 | 2.35 | 8.65 | 5.49 | 3.82 | 5.13 |
4.2.1 The impact of delayed flights and missed connections/flights
EU connections | Delayed arrival at the intermediate airports (minutes) | |||||
---|---|---|---|---|---|---|
10 | 20 | 30 | 40 | 50 | 60 | |
Alliances | ||||||
OneWorld | 13.5% | 27.0% | 38.5% | 50.0% | 58.8% | 67.9% |
SkyTeam | 13.0% | 26.1% | 39.0% | 51.0% | 61.6% | 70.8% |
Star Alliance | 13.8% | 26.6% | 39.5% | 51.7% | 62.6% | 72.2% |
Online | 21.5% | 34.5% | 43.9% | 51.4% | 58.6% | 63.1% |
Self-connect | 14.5% | 28.3% | 41.1% | 52.8% | 62.6% | 70.7% |
Total connections | 14.2% | 27.7% | 40.3% | 52.0% | 62.0% | 70.6% |
Extra-EU connections | Delayed arrival at the intermediate airports (minutes) | |||||
---|---|---|---|---|---|---|
10 | 20 | 30 | 40 | 50 | 60 | |
Alliances | ||||||
OneWorld | 7.8% | 15.7% | 23.7% | 31.8% | 39.3% | 48.1% |
SkyTeam | 8.1% | 16.7% | 26.3% | 36.0% | 46.0% | 55.5% |
Star Alliance | 8.0% | 16.7% | 26.1% | 36.3% | 45.7% | 54.6% |
Online | 5.6% | 10.2% | 18.9% | 24.1% | 29.0% | 31.8% |
Self-connect | 13.5% | 25.2% | 36.5% | 46.4% | 55.9% | 64.4% |
Total connections | 10.6% | 20.5% | 30.4% | 39.9% | 49.1% | 57.8% |
Missing first-step flight | OneWorld | SkyTeam | Star Alliance | Online | Self connect | Total |
---|---|---|---|---|---|---|
European Connections | ||||||
No. travels completed | 21,968 | 36,767 | 43,600 | 3153 | 80,400 | 185,888 |
% of total O-D connections | 79.6% | 89.0% | 82.3% | 68.6% | 56.5% | 69.2% |
Delay at destination (h) | 14.6 | 12.0 | 10.8 | 19.2 | 20.9 | 16.0 |
Path completed in the day | 10,083 | 19,281 | 25,839 | 991 | 20,543 | 76,737 |
% of travels completed | 45.9% | 52.4% | 59.3% | 31.4% | 25.6% | 41.3% |
Delay at destination (h) | 4.8 | 5.6 | 4.2 | 5.7 | 4.8 | 4.8 |
Extra-EU Connections | ||||||
No. travels completed | 12,853 | 20,030 | 19,660 | 444 | 24,899 | 77,886 |
% of total O-D connections | 75.0% | 79.0% | 73.4% | 73.1% | 64.5% | 71.8% |
Delay at destination (h) | 17.4 | 18.3 | 15.7 | 25.0 | 22.6 | 18.9 |
Path completed in the day | 3933 | 5280 | 7159 | 48 | 3714 | 20,134 |
% of travels completed | 30.6% | 26.4% | 36.4% | 10.8% | 14.9% | 25.9% |
Delay at destination (h) | 6.8 | 5.5 | 4.5 | 16.1 | 5.2 | 5.3 |
Total Connections | ||||||
No. travels completed | 34,821 | 56,797 | 63,260 | 3597 | 105,299 | 263,774 |
% of total O-D connections | 77.9% | 85.2% | 79.3% | 69.2% | 58.2% | 69.9% |
Delay at destination (h) | 15.6 | 14.3 | 12.4 | 19.9 | 21.3 | 16.9 |
Path completed in the day | 14,016 | 24,561 | 32,998 | 1039 | 24,257 | 96,871 |
% of travels completed | 40.3% | 43.2% | 52.2% | 28.9% | 23.0% | 36.7% |
Delay at destination (h) | 5.4 | 5.6 | 4.2 | 6.2 | 4.9 | 4.9 |
5 Conclusion and discussion
- Self-connections take longer to be completed in terms of the quickest alternatives, and also with respect to the other kinds of connections (see Table 3), even if their differences in travel times range from 2% to 3%, which is much less than one would expect.
- In terms of frequencies, self-connecting passengers have, on average, fewer alternatives to complete a given O-D pair than in the case of alliance-based connections. The difference in their frequencies is generally around 33% (see Table 4).
- Self-connections lag well behind other kinds of connections in case of daily return trips. This is mainly due to the fact that self-connections are generally not symmetric and are therefore unlikely to allow completion of a round trip, especially during a day (see Table 5).
- When considering round trips in which passengers spend at least 1 day at their destination, the difference between self-connections and alliance-based connections is significantly reduced. However, in the latter case, there are at least twice as many options available for passengers for the return trip compared to self-connections.
- The percentage of missed connections to extra-EU destinations when the incoming flights are delayed is significantly higher for self-connecting passengers.
- The higher frailty of self-connections is also evident while examining consequences for passengers who missed a flight in their trip. If self-connecting passengers miss the first-leg flight of their trip, the probability of reaching the final destination is reduced in comparison to other kinds of connections. Even in cases where self-connecting passengers can reach the final destination within 48 h, the incurred delays are almost double that of other types of connections. Passengers generally arrive at a destination about 21 h after they had planned to do so (see Table 8).
- Similar results are obtained in the scenario of passengers missing the second-leg flight of their trip. Even if the advantages of alliance-based connections are reduced in comparison to the previous case, the risk of not making the O-D trip within 48 h, and the incurred delays are still significantly higher for self-connections than for alliance connections (see Table 9).
Missing second-step flight | OneWorld | SkyTeam | Star Alliance | Online | Self connect | Total |
---|---|---|---|---|---|---|
European Connections | ||||||
No. travels completed | 24,300 | 37,787 | 46,597 | 3919 | 109,425 | 222,028 |
% of total O-D connections | 88.1% | 91.5% | 87.9% | 85.3% | 76.9% | 82.6% |
Delay at destination (h) | 8.5 | 7.7 | 7.2 | 12.7 | 12.1 | 9.9 |
Path completed in the day | 15,472 | 24,337 | 32,691 | 1884 | 53,232 | 127,616 |
% of travels completed | 63.7% | 64.4% | 70.2% | 48.1% | 48.6% | 57.5% |
Delay at destination (h) | 4.0 | 4.3 | 3.8 | 4.8 | 4.1 | 4.1 |
Extra-EU Connections | ||||||
No. travels completed | 13,463 | 20,426 | 19,774 | 520 | 29,110 | 83,293 |
% of total O-D connections | 78.6% | 80.5% | 73.8% | 85.7% | 75.4% | 76.8% |
Delay at destination (h) | 16.7 | 18.0 | 20.8 | 19.4 | 21.2 | 19.6 |
Path completed in the day | 4479 | 5387 | 2763 | 104 | 5025 | 17,758 |
% of travels completed | 33.3% | 26.4% | 14.0% | 20.0% | 17.3% | 21.3% |
Delay at destination (h) | 11.3 | 7.3 | 12.3 | 19.4 | 11.0 | 10.2 |
Total Connections | ||||||
No. travels completed | 37,763 | 58,213 | 66,371 | 4439 | 138,535 | 305,321 |
% of total O-D connections | 84.4% | 87.3% | 83.2% | 85.4% | 76.6% | 80.9% |
Delay at destination (h) | 11.5 | 11.3 | 11.2 | 13.5 | 14.0 | 12.6 |
Path completed in the day | 19,951 | 29,724 | 35,454 | 1988 | 58,257 | 145,374 |
% of travels completed | 52.8% | 51.1% | 53.4% | 44.8% | 42.1% | 47.6% |
Delay at destination (h) | 5.6 | 4.8 | 4.5 | 5.6 | 4.7 | 4.8 |