Two Airlines on One Route

Summary

On 944 routes where two airlines that sell their own seats each flew enough to compare, the two differed in on-time arrival by a median 4.9 points when compared only in the departure windows they share (5.5 over the whole route), and by 10 points or more in 18.4% of 1,721 pairs. The difference lasts: the airline ahead in the even-numbered months was ahead in the odd-numbered ones in 87.1% of pairs, and in 99.6% of the pairs where the gap was large. United Airlines came out 6.6 points ahead of the airlines it met and Frontier Airlines 4.9 behind. A hub carrier had no edge on the routes leaving its own hub.

A pair is two airlines that both sell their own seats and both fly the same origin and destination: American Airlines, Alaska Airlines, JetBlue, Delta Air Lines, Frontier Airlines, Allegiant Air, United Airlines and Southwest Airlines. Regional carriers that fly for a larger airline are not in the pairs, because a passenger does not choose them, and they get their own section below. Each airline’s flights on a route are sorted into the site’s six departure windows. The two airlines are compared only in the windows where both have at least 120 flights, and their on-time rates are averaged over those windows with the same weights, so the same windows count the same amount for each. The route, the time of day and the season are then the same for both. An airline counts as flying a route with at least 200 flights on it, and a pair is used when each airline has at least 500 flights in the windows the two share. The gap is the better airline’s on-time rate minus the other’s. The whole-route gap is the same difference taken over every flight the two flew on the route, which is what a route page shows.

1,721 pairs on 944 routes. The gap is taken without its sign, so it says how far apart two airlines are and not which is ahead. The median is 4.9 points matched and 5.5 over the whole route.

Two airlines on one route often fly at different times, and the evening is worse than the morning, so part of a gap could be timing. Matching the windows changes the median gap from 5.5 to 4.9 points. It does change who is ahead in 266 pairs, 15.5% of them, and those pairs were close to begin with: their median whole-route gap was 2.2 points. Nor is it chance. Splitting the months into even-numbered and odd-numbered, so that both sets run through the whole year, 1,379 pairs had enough flights in both sets to compare. The same airline led in both in 87.1% of them. Of the 282 pairs that led by 10 points or more in the even-numbered months, 281 led again in the odd-numbered ones, and the average gap there was still 12.2 points. Each set needs at least 250 matched flights per airline.

Months are split into even-numbered and odd-numbered. Pairs are grouped by how far apart the two airlines were in the even-numbered months, and the odd-numbered months are read from the point of view of the airline that led in the even-numbered ones, so a positive figure means it kept its lead. A group needs at least 30 pairs.

For each airline, the table averages its matched gap over every pair it is in, weighted by its own flights in the shared windows. A positive figure means that on the same routes in the same windows it beat the airlines it met by that many points. United Airlines is highest at +6.6 and Frontier Airlines lowest at -4.9. Two things separate this from the whole-network ranking: an airline is compared only where it has company, and only in the windows it shares. American Airlines moves from fifth to third and Alaska Airlines moves from third to fifth. An airline that mostly meets strong rivals is held to a higher standard than one that meets weak ones, so the figure is a comparison with the field an airline actually faces and not a score against all carriers. An airline appears with at least 30 pairs.

Ordered by the figure against the airlines it meets. On time is the share of flights that arrived fewer than 15 minutes late. Carriers that did not report every month are not compared.

An airline is the hub carrier at an airport when it has the largest share of its departures, at least 40%. On the routes that leave a hub carrier’s own hub, the hub carrier was ahead of the rival in 50.2% of 325 pairs, by a median +0.1 points. On routes that arrive at its hub it was ahead in 60.6% of 315, by a median +1.5. Flying out of its own hub gives an airline no measurable edge over a rival flying the same route at the same time. The airport-level view understates hub carriers. Set against every other airline at the airport, a hub carrier’s on-time rate looks lower than it does against rivals on the same routes in the same windows: at 13 of 17 hubs the matched gap is higher than the raw one, by a median 1.8 points. The raw figure sets a hub carrier’s whole schedule against everyone else’s whole schedule, and the matched figure sets them against each other only where they fly the same route at the same time.

Pairs where one airline is the hub carrier at an end of the route and the other is the hub carrier at neither. A group needs at least 30 pairs.

Departures from the airport. The first gap is the hub airline’s on-time rate minus the other compared airlines’ rate over every flight from the airport. The second compares route by route and window by window, weighted by the hub airline’s flights, where both have at least 120. The last column is the share of the hub airline’s departures that had a rival in the same route and window; a hub is shown when it is at least 25%. The 15 largest are shown.

Some regional carriers fly for exactly one airline, so a passenger who buys that airline’s ticket may end up on either. Envoy Air and PSA Airlines fly only for American Airlines. Where the airline and its regional partner both fly a route in the same windows, Envoy Air arrived on time more often than American Airlines on 93.9% of 115 routes, by a median 8.8 points; PSA Airlines arrived on time more often than American Airlines on 65.1% of 109 routes, by a median 1.9 points. Most of Envoy Air’s routes run through DFW, where the median gap is larger, +11.5 points; away from it Envoy Air was ahead on 87.0% of 54 routes, with a median gap of +5.9 points. Most of PSA Airlines’ routes run through CLT, where the median gap is larger, +2.4 points; away from it PSA Airlines was ahead on 57.1% of 56 routes, with a median gap of +0.7 points. Both are sold under the airline’s name. The comparison holds the route and the time of day fixed and does not hold the aircraft, the terminal or the crew.

Routes where both have at least 500 flights in the windows they share. A pair of carriers needs at least 30 such routes to be shown.

Routes where the gap is at least 5 standard errors wide and each carrier has at least 500 flights in the shared windows, widest first.

648 pairs have a gap wide enough to name: at least 5 standard errors, with 500 or more flights per airline in the shared windows. The widest is DEN to PHL, where United Airlines arrived on time 88.3% of the time and Frontier Airlines 57.2% in the same windows. Among the 317 pairs that differ by 10 points or more, Frontier Airlines and Southwest Airlines are the lower airline in 62% and United Airlines and Delta Air Lines the higher in 76%, so the large gaps come mostly from a few airlines meeting each other.

On-time rates are over the departure windows both airlines fly on the route. The 15 widest of 648 pairs, widest first.

The six windows are wide, so two airlines in the same window can still fly at different hours of it, and the comparison does not hold the day of the week fixed. It cannot see aircraft size, terminal, gate or crew, which differ between airlines and affect on-time arrival. It counts the airline that operated a flight, so a flight sold by one airline and flown by another appears under the operator. Endeavor Air, Hawaiian Airlines and Spirit Airlines did not report every month. SkyWest Airlines and Republic Airways fly for more than one airline, and the data does not say which one sold a given flight. They are not compared. A route with one airline has no comparison, and the routes with two or more are the busier ones. A gap is an average over the whole period and is not a forecast for a particular flight.