The Reagan administration, citing serious concerns over security at National and Dulles International airports, announced substantial pay increases yesterday for the federal police officers charged with ensuring the safety of passengers at both airports.

A senior administration official, who asked not to be named, said White House chief of staff Donald T. Regan personally endorsed the pay increases of up to 22 percent for the Federal Aviation Administration police force. Officers on the force long have contended they are so poorly paid that airport security airports is questionable. Tuesday, the day before a bomb exploded aboard a TWA flight over Greece, they mounted a renewed media campaign on the issue.

Administration officials said the decision to grant the pay increases came in response to a Tuesday letter from Transportation Secretary Elizabeth Hanford Dole and was not prompted by concerns over terrorism or the TWA bombing.

"Everyone in this administration from the president on down wants to assure that travelers at those airports are safe," Constance Horner, director of the Office of Personnel Management, said as she announced the raises.

The increases, ranging from $727 to $3,360 a year, have been sought for years by the FAA. Dole has said that low pay -- no police force in the metropolitan area pays its officers less -- has made it nearly impossible to retain qualified staff members for more than a year or two.

There are 97 officers and 37 vacancies on the force charged with guarding National and Dulles, the only two commercial airports in the nation owned and operated by the federal government.

Yesterday, in part because of new security measures that have been adopted to counter potential terrorists, police at National evacuated part of the North Terminal after bomb-sniffing dogs reacted positively to an unclaimed package in a bathroom. Police said the package turned out to be a pound of cocaine, surrounded by nitrate -- an ingredient in gunpowder.

"We have been working hard on this security and pay issue for a long time," said Stephen Hayes, the FAA's assistant administrator for public affairs. "Of course, by itself the pay raise is not the whole answer to security, but it's an important step and we're very pleased."

Tuesday, the same day several FAA police officers called a news conference at Dulles to complain about security, Secretary Dole wrote Horner asking for immediate response to what Dole called "the critical staffing and pay problems that continue to exist" for police at the airports. She wrote that despite a small pay increase that became effective in January for FAA police, the turnover rate had climbed from 55 percent to 66 percent.

"The vacancy rate which FAA continues to experience despite the January salary increase clearly is unacceptable with the increased emphasis on security at our airports," the letter stated.

Yesterday's increases, most of which were for the maximum amount allowed under present law, are not permanent, according to OPM. As a rule, special pay increases are reviewed once a year and can be adjusted at that time.

In 1985 the minimum starting salary for an FAA police officer was $14,298. In January that figure rose to $14,578, and yesterday's announcement will put the salary at $16,723. By comparison, the starting pay for an officer with the National Zoological police is $17,221. In Alexandria minimum starting pay for a new police recruit is $20,262.

Under FAA regulations, airlines handle screening of passengers and carry-on luggage at all public airports in the country. But the airport operator, most often a city, is responsible for other security measures, such as protecting aircraft and enforcing laws.

"The men who guard these airports and the thousands of people who use them each day are finally being recognized," said Lt. Thomas Holderness, the FAA station commander at Dulles. "The stress and the overtime have been overwhelming and this should help."

At her news conference Horner said, "There is something wrong with the federal pay structure" when the law interferes with security needs.