Airlines reported 302 tarmac delays longer than three hours on domestic flights, compared with 202 in 2018 and 193 the year before. There were 26 delays of more than four hours on international flights, compared with 61 the year before and 51 in 2017.

According to federal rules, airlines can hold passengers on the tarmac for three hours on domestic flights and four hours on international flights before allowing them to get off.

The longest tarmac delay for a domestic flight in the last month of the year occurred on Dec. 18, when passengers aboard a United plane waited four hours and seven minutes at Newark Liberty International Airport for a flight to San Diego. The same day, passengers aboard another United flight headed to Milan waited more than five and a half hours on the tarmac at Newark, the longest such delay for an international flight in December.

“United is disproportionately impacted by severe weather when compared to our competitors, based on the geographic location and size of our busiest hubs — particularly Newark,” the airline said in a statement. “Additionally, we are seeing worsening weather and much more intense and longer-duration weather events.”

Last year was the worst in United’s history in terms of delays caused by weather or air traffic control, it added.

Airlines for America, a trade group, said airlines carried a record number of passengers last year, adding that the tarmac delays were caused by severe weather, airport maintenance and construction work and security-related disruptions.

Delays are one thing, though. Never boarding the flight you booked is another.

According to figures released Wednesday, the major carriers canceled 1.9 percent of scheduled flights last year, a figure that has steadily increased since hitting a low of 1.1 percent in 2016. And cancellations were highest at American Airlines, Southwest Airlines and United, which have had to scrap hundreds of flights because of the grounding of the Boeing 737 Max.