They might have been a couple of starry-eyed flyboys with their heads in the clouds. Upon closer inspection, they turned out to be a couple of Saudi Arabian princes, one the ambassador to the United States and the other Saudi Arabia's first man in space.

Prince Bandar Bin Sultan, the ambassador, could hardly contain his envy.

"I think I should be the first diplomat in space," he said, eyeing his equally royal cousin, Prince Sultan Salman Saud, a major in the Saudi air force. "I tell you," Bandar added with a confiding note, "flying beats the hell out of being an ambassador."

Last night, at least, Bandar did his duty as diplomat by introducing Sultan and his commander on the space shuttle Discovery, Navy Capt. Daniel C. Brandenstein, to 200 guests from the Saudi and American aerospace communities, Arab-world embassies, the U.S. Congress and the media. Earlier in the day, he introduced Sultan and Brandenstein to President Reagan at the White House.

Later this week, Sultan begins a tour of several American cities. He and others in Discovery's crew, which included the first French astronaut, recently completed a tour of France. Saudia Arabians may get their chance to see the crew in December.

"The whole country is waiting for them," Sultan said.

Meanwhile, next month Sultan starts his training in flying F-15 fighter planes like those Saudi Arabia hopes to buy from the United States in an arms package estimated to cost more than $1 billion.

"You should give them to us, we're the good guys," Sultan said of the proposed sale, which has already resulted in "very strong objections" from the Israeli government.

Sen. Richard G. Lugar (R-Ind.), chairman of the Foreign Relations Committee, warned Secretary of State George Shultz last week that a Saudi arms sale and a similar $1 billion package for Jordan would be "counterproductive."

Bandar, who ran the Saudis' highly successful AWACS lobbying effort four years ago, said he is working "with the administration" on the new arms sale package, although it's "nothing new."

"We've been working on it for many years because it's an ongoing thing," he said. "We will continue to work with our American friends."

Harry J. Gray, chairman and chief executive officer of United Technologies, which makes the F-100 engine for the F-15 airplane, said Saudi Arabia has "a lot more friends" than it did four years ago during the highly controversial AWACS fight. As a result, he predicted the Saudis' lobbying efforts will be "more subtle."

There may have been some of that going on last night, but for the most part it seemed to be a case of undisguised elation among the Saudis that one of them had made the Discovery orbit.

NASA's James M. Beggs called Saudi Arabia's participation "enormously important" because it brings the international community into the program.

"I got up very early this morning to go out to Goddard to encounter a comet, and we did indeed succeed in flying through the tail of a comet," Beggs said of the International Cometary Explorer, which intercepted the comet Giacobini-Zinner 44 million miles above Earth.

"It is the age of astronomy -- space astronomy especially," said Beggs, adding a historical note that especially pleased the Saudis. "When you think about it, most of the important stars have Arab names and that's because the early astronomers were Arabs."