American Airlines was warned that it did not have enough pilots to execute its ambitious summer flying schedule, the carrier’s union said, after the cancellation of hundreds of flights drew the ire of passengers.

The Fort Worth, Texas airline said this week that it would scale back its re-expansion plans after shortcomings were revealed by bad weather over the weekend. Staff shortages meant it could not quickly recover from weather disruption at its main hubs, forcing dozens of flights to be cancelled.

American has been the most aggressive of the three largest US carriers to add flights back to its schedule. Boosted by resurgent demand in the domestic market, American planned to sell only 5 per cent fewer seats in July than it did in 2019.

The company said on Monday that it was cutting about 1 per cent of its scheduled flights through to mid-July in order “to build in additional resilience”, underscoring the tricky task of carriers in scaling back up activity as the coronavirus pandemic wanes.

The Allied Pilots Association, which represents 15,000 pilots at American, said it had warned the airline that it was understaffed as a result of the furlough of employees it briefly imposed and the voluntary leave and early retirements it had accepted to get through the pandemic.

“We were warning them, ‘Hey, this [staffing level] is likely to be very strenuous on us when a weather event happens,’” said Dennis Tajer, the APA’s communications committee chair. “We don’t have enough pilots.”

Unlike rival airlines United and Delta, American briefly furloughed 1,600 of its pilots during a lull in receiving funds from the federal government’s Payroll Support Program, which was meant to buoy the airline industry through the pandemic when passenger numbers plummeted.

That made it more difficult to return pilots to active status immediately because US Federal Aviation Administration regulations require fresh training, Tajer said. The airline also had 1,000 pilots retire early.

The airline’s decision to retire 100 aircraft prompted further training requirements, so pilots could learn to fly a different jet. The airline’s training centre in Dallas-Fort Worth was “under great stress”, Tajer said, with the airline needing to rent off-campus simulator time.

“We’re elated that we’re flying so much, and we’re frustrated that we’re not getting the tools,” he said, before reaching for a baseball analogy. “They say ‘Batter up!’ and hand us a hockey stick.”

Bad weather has disrupted American hubs including Chicago, Miami, Dallas-Fort Worth and Charlotte, on nine of the first 15 days of June. That hampers an airline’s ability to effectively deploy planes and crews and effects can linger in the system when the available pilots and flight attendants butt up against rest periods mandated by federal regulations.

About a third of the cancellations American logged between June 18 and June 21 were because a flight crew was unavailable, according to a company report, the most common reason on all but one of those days.

“The first few weeks of June have brought unprecedented weather to our largest hubs, heavily impacting our operation,” the airline said. “We made targeted changes with the goal of impacting the fewest number of customers by adjusting flights in markets where we have multiple options for re-accommodation.”

Savanthi Syth, an analyst at Raymond James, said that without the Payroll Support Program — which distributed $63bn to airlines, including $12.8bn to American — more carriers would be struggling to accommodate the sudden surge in demand for domestic US travel.

“This is PSP doing its job,” she said. “Otherwise we would be in a much worse position than we are today.”

American’s decision to cut flights was “better than stranding people”, she said. “They saw the network needed more cushion.”