New York Air may have to delay the start of its low-fare service between Washington and New York because of the work still remaining to satisfy federal safety standards, Federal Aviation Administration officials said yesterday.

In a related development yesterday, the Civil Aeronautics Board gave its final approval to the creation of New York Air, finding the affiliate of Texas International Airlines fit and its proposed services in the public interest.

The CAB is the agency with the authority to give airlines their route and overall fitness certificates, while the FAA decides on whether airlines meet federal safety/fitness standards.

FAA officials haven't found New York Air unfit but said yesterday the airline would be hard-pressed to complete FAA requirements in time to get an operating certificate by Sunday, the day New York Air planned to begin its operations.

New York Air officials were optimistic yesterday that they would be operating on Sunday. But in the "unlikely event" of a delay in certification, they said that any passenger booked on NYA who presents herself or himself at NYA's ticket counters will be assured by NYA of getting on another airline's flights.

"There are a number of items not completed yet," Lonnie Parrish, deputy regional director of the FAA's eastern region, said yesterday. "We don't doubt that they will complete them, but whether they can in the time allowed is another question. They've been very professional about it so far and have been very impressive with their performance so far, but there is still quite a bit of work to do and a very short time in which to do it."

Parrish said the remaining area, such as spelling out the airline's policies and procedures in sufficient detail, providing the FAA with the names of people who will serve in certain capacities and supplying documentation for New York Air's contractual arrangements with others to do required maintenance when NYA itself will not be doing it.

For instance, New York Air has contracted to have Trans World Airlines perform maintenance and provide ground-handling support at Washington's Airport, but the FAA has determined that TWA personnel are not sufficiently experienced with the DC9 aircraft NYA will be flying. "Our pronouncement, there, was that an experienced DC9 person from New York Air would have to supervise the Washington operation until the time that Twa people could gain the necessary experience level," Parrish said.

Parrish said he wouldn't want to estimate how long it would take for NYA to complete the FAA requirements. Although the inspectors may be interested in helping meet a deadline, Parrish said, the FAA feels no time pressure. "The only mission we have is to make sure the airline meets all the requirements to the letter before we issue them a certificate," he said. "Until they do, we will simply not issue them a certifcate."

In addition to getting its FAA certificate, New York Air also needs to work out a satisfactory arrangement with the Department of Transportation to operate a full complement of 10 round-trip flights a day it has scheduled.

Because NYA was successful in gaining only 18 slots -- permitted takeoffs and landings -- at National, it made plans to operate the other two flights "subject to air traffic control." That would mean operating them during good weather when the so-called visual flight rules prevail; the high-density rule allows extra flights to land in those conditions.

During bad weather when instrument flight rules prevail, NYA would cancel the flights and put it's passengers on the Eastern Air-Shuttle at NYA's expense, NYA officials said. Earlier this week, DOT officials objected to NYA's plan and considered having NYA fly the two flights as "extra sections" exempt from the slot limits; now, they think NYA's first plan might be the most appropriate -- and legal.

Meanwhile, New York Air yesterday christened it first plane and graduated its first group of employes at ceremonies at New York's LaGuardia Airport. i