Charging that airlines have lost sight of safety and service, a Senate panel yesterday told President Reagan's nominee to head the Federal Aviation Administration that he will inherit "a system in crisis."

T. Allan McArtor did not say specifically how he would resolve the crisis, but testified at his confirmation hearing that he would not "compromise the margin of safety in an effort to reduce {flight} delays."

The 44-year-old Federal Express executive glided through the two-hour hearing before the Commerce, Science and Transportation subcommittee on aviation, receiving strong endorsements from members. McArtor is expected to gain approval by the full Senate in two weeks.

Senators used the session to vent their exasperation with the aviation industry and to set down a gauntlet for the FAA. Unless McArtor succeeds in "shaping up" the airlines, several members said, Congress may enact new industry regulations as early as September.

"I believe the public is being lied to again and again and again," Sen J. James Exon (D-Neb.) said, accusing commercial carriers of knowingly posting unrealistic flight schedules. "If it isn't straightened out, the airlines are inviting reregulation of the system," he said.

Senators acknowledged that McArtor's task -- to improve safety while reducing delays -- might seem like a mission impossible.

"You've got a crisis on your hands," Sen. Ernest F. Hollings (D-S.C.) said, adding, "I hope you're just as smiling and young looking next year as you are now."

McArtor said his first priority would be to make sure the FAA "is doing everything possible" to ensure aviation safety, and said he would try to restore confidence in the system by being "a better communicator."

McArtor, who served as a fighter pilot in Vietnam, would succeed Donald D. Engen, who resigned as FAA administrator last March, reportedly frustrated by interference from the Transportation Department.

Engen became caught up in a dispute with the National Transportation Safety Board over its warnings of an "erosion of safety" in aviation. Yesterday, McArtor pledged to "take all NTSB recommendations seriously" and said when air traffic becomes excessive he "will not hesitate to impose whatever temporary procedures may be necessary until safety can be verified."