Aviation Airline complaints pile up in April By Robert Silk / June 14, 2017 Share 1 -- The number of formal complaints filed against the airlines jumped 70% in April, the Department of Transportation reported Wednesday. A total of 1,909 complaints were filed, up from 1,123 complaints in April 2016. The 1,909 complaints were also up 69% from March of this year. The number of complaints about flights (cancellations, delays, misconnections) more than doubled from the previous April, from 372 to 753. Delta had 201 of the flight complaints, almost twice as many as runner-up American, which had 106. Severe thunderstorms in early April in Atlanta caused Delta to cancel nearly 4,000 flights over five days. Across all categories of complaints, American had the most at 324. Spirit Airlines by far had the worst proportion of complaints with 7.2 complaints per 100,000 enplanements; United was second worst at 3.04.