Some regional carriers are doing better keeping their flights on time than industry behemoths such as American Airlines and Southwest Airlines, according to a first peek at new data compiled by federal regulators.

A U.S. Department of Transportation report released Tuesday is the first to include details on regional carriers, a huge part of the airline industry that was absent from the department’s performance surveys for several decades. This year, more than half of domestic flights were on regional airlines or “branded codeshare partners” as DOT terms them, carrying about one-quarter of U.S. air travelers. 

In July, four large regional airlines — SkyWest Inc., Endeavor Air Inc., ExpressJet Holdings Inc. and Republic Airlines Inc. — delivered a better on-time percentage than American, United Continental Holdings Inc., Southwest and JetBlue Airways Corp.

SkyWest ranked fourth across the industry, with 80.4 percent of its flights on time. Utah-based SkyWest, the largest U.S. regional airline, owns ExpressJet; Delta owns Endeavor. Mesa Air Group Inc., which flies for American and United, also placed among the top five carriers in some months going back to the spring.

The three largest U.S. airlines, plus Alaska Air Group Inc. and Hawaiian Holdings Inc., use regional airlines to fulfill large parts of their flight schedules.

With the new report, “the flying public will see a more complete picture of the performance of scheduled passenger service,” the department said in a news release. Regulators required airlines to begin reporting the data in January, though it wasn’t released until now because it was being reviewed for accuracy, the department said.

The data suggest that U.S. airlines have made a concerted effort in 2018 to boost the reliability of their regional partners, which fly smaller, 50- to 100-seat jets to feed traffic into the larger carriers’ hubs.

Regional airlines still have higher rates of cancellations than the major airlines. That’s because the smaller planes get scrubbed before the larger ones in cases where airlines have to limit flights because of bad weather or airport congestion.

Delays continue to bedevil JetBlue Airways Corp., with only 69.1 percent of its flights on time so far in 2018. That put New York-based JetBlue behind industry peers including two ultra low-cost carriers, Allegiant Travel Co. and Frontier Airlines. Representatives for JetBlue did not respond to e-mail requests for comment.

American, the world’s largest carrier, lagged Delta Air Lines Inc. and United in terms of its overall network’s on-time performance, at 77.2 percent this year. That compared to 82.5 percent for Delta and 78.4 percent for United. Delta’s regional carriers also flew more of their flights on time than the regionals at American and United.

Hawaiian Airlines topped the industry’s on-time ranks this year through July, followed by Alaska, which has largely completed its integration of Virgin America. Delta was third.

Late-arriving aircraft was the top reason for delays, at 8.4 percent, followed by congestion issues in the national aviation system, at 6.7 percent, according to DOT. Airlines’ own delays accounted for 6 percent of late flights.

The industry also continued to shrink the number of passengers who are denied boarding because of overbooked flights or other operational issues. The practice drew attention last year after a man was dragged from a United Express flight when he refused to get off the plane voluntarily.