(CNN) — The steepest downturn in modern aviation history means plenty of airline pilots are spending weeks or months of the coronavirus pandemic idling at home.
When they do return to the cockpit, a few are admitting that they're out of practice, and knocking off the rust is proving harder than anticipated.
"This was my first flight in nearly 3 months," one pilot wrote in a June report explaining why he or she neglected to turn on the critical anti-icing system. "I placed too much confidence in assuming that it would all come back to me as 'second nature.'"
The report on that flight, which landed without incident, is one of more than two dozen documenting the challenges of returning from pandemic-related leave filed in a federal system for tracking aviation mistakes.
A CNN analysis of the publicly available reports, which were highlighted in a recent report by the Los Angeles Times, found returning pilots acknowledging their skills were not as sharp as they expected. The idea behind the NASA-run Aviation Safety Reporting System is that coming clean about errors allows for analysis and improvements that make aviation safer. The reports are stripped of identifying information -- such as which airline and which airports were involved -- and made public in a government database.
"Everyone knows that flying skills and company policies/procedures are highly diminishable," the pilot wrote in the anti-icing report. "In order to prepare for a flight following a period of inactivity I should have dedicated more time to review my duties."
Airlines and the Federal Aviation Administration do have systems in place to require pilots keep in practice. The pilot nearing three months without a flight was fast approaching a federal rule that requires additional training for pilots who aren't active enough over a 90-day period.
The risk, aviation safety expert Peter Goelz says, is that aviation disasters are often at the end of a chain that begins with a simple mistake.
"These kinds of fairly mundane -- what appear to be mundane -- errors can really result in terrible events," said Goelz, who is a CNN aviation analyst and former managing director of the National Transportation Safety Board, which investigates crashes.
'Boy was I wrong'
One of the most serious issues identified in the reports was a plane that landed without permission from air traffic controllers. The pilots of that flight were overwhelmed with turbulence and other distractions while approaching the airport, one of the pilots wrote, and they "forgot to obtain the landing clearance."
"Since COVID-19 breakout, I was not flying as frequently as before," that pilot wrote. "I believe this was factored into this incident."
Several pilots reported drifting from their assigned altitude, and one documented aiming for the wrong runway -- decisions that, had another plane been nearby, could have led to a collision.
One said that after a smooth first flight in several months, he or she was surprised to make a mistake managing the airplane's speed.
"I thought I was through the danger of being rusty, boy was I wrong," the pilot wrote. "I wrongly figured I had knocked the rust off ... when the first leg went so well."
Several pilots reported incorrectlry programming flight computers or radios. One captain who reported dialing in the wrong frequency while approaching an airport said he or she "hadn't flown for two months;" in the other seat was a colleague who "hadn't flown for 6 weeks."
"I struggle to see a viable remedy for this problem besides just flying more, which the current situation may or may not allow soon," the captain wrote. "We definitely need to be more aware of how much our proficiency decreases as we are flying less."
On any given day, about 400 pilots filter through American Airlines' training programs. Preparation for mock flights in massive flight simulators begins before the sun rises, and the final simulated landings take place after midnight.
Jim Thomas, a captain with 35 years of experience who now leads flight training and standards at American, said his team is no stranger to pilots returning from leaves of absence. Some pilots spend time away from the cockpit for medical or personal reasons, and others return to the company after being called up for military service.
"Where we would normally be training long-course pilots to learn new aircraft, in this case we're getting them requalified," Thomas told CNN in an interview. "We're not going to allow them to go fly the line until they're fully trained and ready to go fly."
At a facility in Dallas, and another in Charlotte, North Carolina, pilots file into classrooms for instruction, and into simulators to practice their skills. In one classroom, an instructor walked pilots through slides about programming the flight director computer. Nearby, pilots were flying scenarios in the simulator -- large rooms propped up on hydraulic legs that look, from the outside, like white space capsules.
Curtis Joens is an American captain who recently returned from a four-month leave of absence -- the first of his three-decade career. Joens said that as a more senior pilot, he took some time away from the job to give lower-ranked pilots an opportunity to keep flying.
Joens said he studied before brushing up on his skills at the training center. He said one instructor commented after a simulator ride that his time away from the cockpit wasn't noticeable.
Key to safe flight, Joens said, is the methodical way pilots approach their work.
"We don't just sit down and say, 'OK, start engines,' and fly by the seat of our pants," he told CNN. "There's a checklist and a methodology for everything that we do, all the way from the preflight to starting engines, to taxi, to takeoff."
American analyzed its pilots and insists the pandemic has not led to a decline in their skills.
Joens also said pilots have a conversation before the flight to talk about any concerns, which would include time away from the job. "Just realize you've got two pilots up there, they're supporting one another, they're watching one another, they're challenging one another," he said.
Airlines are currently flying about 45% fewer flights than usual, according to the industry group Airlines For America. But the industry is hopeful travel will recover as more people receive coronavirus vaccines. That type of uptick is what it will take for larger numbers of pilots to return to flying. In the meantime, it is an issue airlines will monitor.