WASHINGTON — A fatal UPS cargo plane crash during a landing attempt last year was caused by pilots who made a series of errors and should have aborted the landing, the National Transportation Safety Board said Tuesday.

The panel also said the pilots may have been suffering from fatigue, but said more stringent federal rules governing pilot hours wouldn’t have prevented the accident. Such tightened rules are being sought by the pilots’ union and are being resisted by UPS.

The primary cause of the pre-dawn accident on Aug. 14, 2013 was the pilots’ decision to continue a landing attempt at Birmingham-Shuttlesworth Airport in Alabama after they realized the plane wasn’t lined up correctly — and their failure to monitor the plane’s altitude — the board said.

The twin-engine Airbus A300 descended too rapidly, clipping the tops of trees and crashing into a hillside just shy of the shorter of the airport’s two runways.

Capt. Cerea Beal, 57, of Matthews, North Carolina, and First Officer Shanda Fanning, 37, of Lynchburg, Tennessee, were killed. Both pilots had expressed concern about fatigue and work schedules, according to the plane’s cockpit voice recorder, Fanning’s text messages the previous day and Beal’s recent conversations with other pilots.

The board agreed that both pilots had prior opportunity for adequate rest, but were likely fatigued because the flight from Louisville, Kentucky, took place during early morning hours when people naturally crave sleep even if they are well rested. Also, Fanning was likely suffering from acute sleep deprivation because she didn’t take full advantage of her rest opportunities, the board said.

The Independent Pilots Association, which represents UPS’ 2,600 pilots, had previously cited the crash as evidence that more stringent federal rules that govern the work schedules of passenger airline pilots should be extended to cargo pilots as well. UPS has opposed the extending the rules, which went into effect in January.

The Federal Aviation Administration has estimated that extending the rules to cargo pilots, who do much of their flying at night, would cost carriers $550 million over 12 years.

NTSB board member Robert Sumwalt said the board agrees that the more stringent rules should be extended to cargo pilots, but that this was not the accident to make that case.

“The board isn’t going to sacrifice our credibility to make that point,” he said. But Sumwalt also criticized UPS’ safety culture, pointing to a union survey of its members in which 88 percent of pilots said they feared that telling the company they weren’t prepared to fly because of fatigue would invite adverse scrutiny. He also said the company failed to update critical cockpit software that might have warned pilots in sufficient time that they were too close to the ground.

UPS said in a statement that it disagrees with the board’s conclusion that the pilots were suffering “fatigue related to night flying when the (captain) had not flown in 10 days and the first officer was off eight of the previous 10 days. We believe these facts – and others – don’t support such a finding.”

The company also said it will update the software, but noted that the program met federal regulations.

“We know what we heard from pilots on the cockpit voice recorder and survey” about fatigue, said Brian Gaudet, a spokesman for the pilots union. “What it all really reveals is what Sumwalt said — everything UPS does is about efficiency. Their safety culture is flawed.”

One of the key mistakes made by the captain, the board said, was incorrectly programming the plane’s flight management computer. As a result, the computer was unable to help the pair with the landing, and the pilots didn’t attempt to abort the landing.

The pilots also didn’t call out important altitude levels as the aircraft descended, according to the board.

The airport’s main runway, which is 12,000 feet long, was closed for repairs. The UPS pilots were trying to land on the airport’s second runway, which is 7,000 feet long and has hills at either end. The short runway also lacks complete guidance equipment, making landings there trickier.

Southwest Airlines has since barred its pilots from landing on the shorter runway, and ExpressJet, one of the nation’s largest regional airlines, has urged its pilots to avoid landing on the runway in favor of the main runway whenever possible. An ExpressJet analysis of landings by its own planes on the shorter runway concluded that they come “dangerously close” to nearby hills if they’re only a few feet below their target altitude.