Air traffic controllers said Friday they will be forced to work even when they are tired under a contract the Federal Aviation Administration plans to impose this weekend.

Controller fatigue may be an issue in the investigation of the recent airplane crash in Kentucky that killed 49.

The solo controller in the tower at Lexington Blue Grass Airport had his back turned on the airfield when the pilots took off on the wrong runway early Sunday morning.

He told investigators he had slept only two hours and had worked 17 hours in the past 24.

Sleep researchers say such sleep deprivation typically causes attention lapses and slowed reaction times.

The controllers' new contract with the FAA follows nine months of bitter negotiations that broke down in April. Controllers sought binding arbitration, but the FAA said the law gives it the right to impose its last, best offer.

A section of the contract reads, "Sick leave cannot be granted for rest or minor inconveniences," according to a briefing guide for the FAA's collective bargaining agreement with the National Association of Air Traffic Controllers.

"We would never have a controller controlling traffic who was too tired to work," said FAA spokeswoman Laura Brown.

Brown said a controller can request several different types of leave if he's too tired to direct aircraft. Alternatively, a manager might be able to assign the controller to administrative duties that do not involve controlling air traffic.

"Congress and the inspector general and other oversight agencies have told us that they'd like to see us manage our sick leave better," Brown said. "We have one of the highest sick leave rates in the federal government."

Paul Rinaldi, NATCA executive vice president, said the new work rules will result in tired controllers working when they should not.

On Friday, the FAA's air traffic manager at Washington Center said he would discipline any controller who called in sick because he was fatigued, Rinaldi said.

Rinaldi said controllers cannot work if they are on most types of medication, including over-the-counter drugs. "If I'm taking Sudafed, I cannot work traffic," Rinaldi said.

Air traffic controllers say fatigue is a symptom of a nationwide staffing shortage in the control towers.

Short staffing has forced some controllers to handle double-duty, simultaneously directing airplanes on the ground and monitoring air traffic by radar, much like the controller in Kentucky.

Short staffing also can mean little time to rest between shifts, which also was the case in Lexington.

Two years ago, Los Angeles International Airport's control tower was understaffed by about half the normal level when a tired air traffic controller was involved in the near-crash of two airliners, according to safety investigators.

Several Democratic lawmakers have demanded investigations into the FAA's staffing practices.

On Friday, New Jersey Sen. Frank Lautenberg requested a hearing to determine the risks of short-staffed control towers.

"My personal belief is that the FAA must move swiftly to hire many new air traffic controllers," Lautenberg wrote in a letter to the aviation subcommittee chairman, Sen. Conrad Burns.

The controllers' organization NATCA issued a statement calling the new contract "a brazen, arrogant trampling of the collective bargaining process."

FAA Administrator Marion Blakey has said controllers make much more money than other public servants, control scheduling and hold back modernization.

The union has said the FAA is hostile to controllers and that its contract will result in a wave of retirements because it creates a disincentive for controllers to stay on the job.

Nearly half the current controllers are expected to retire in the next decade. Most of those workers are replacements for the controllers fired by President Ronald Reagan in 1981 for refusing to abandon a strike that he considered illegal.