Pan American World Airways and Air Florida jointly asked the Civil Aeronautics Board yesterday for permission to operate the Braniff International South American routes that the board tentatively gave to Eastern Airlines Monday night.

Within hours, however, the CAB said it couldn't delay formal approval of the Braniff-Eastern agreement because of "the emergency posed by Braniff's financial condition." The board also said it didn't have enough information about the proposal to approve it immediately, and the plan didn't have Braniff's approval.

Pan Am President William H. Waltrip and Air Florida Chairman Eli Timoner contended at a press conference that their proposal would be better than Eastern's plan. The two airlines together propose to pick up and preserve all of Braniff's routes, including those within South America, and start them immediately, they said.

Eastern, which would begin flying the routes on June 1 under its agreement with Braniff, would not preserve Braniff's nonstop flights from the West Coast nor half of Braniff's intra-South American routes, they said. Because Eastern doesn't plan to serve some of Braniff's routes, the United States would lose about 100,000 passengers to foreign airlines, they said. Their plan also would preserve service by two airlines to four of the countries, the two airline officials said.

"We're saying to the CAB: Give Braniff the opportunity to decide which is a better deal for them," Timoner said.

Both Waltrip and Timoner expressed surprise that the board had acted so quickly to approve the Eastern-Braniff deal. "Never in my 23 years in the airline industry have I seen an agreement filed at 4:30 and approved at 8:30 without any ability of the parties to comment on it," Waltrip said.

Timoner said Air Florida and Pan Am had been working around the clock to come up with a proposal, having been told by Braniff that an Eastern proposal probably would come in on Wednesday. "There was not any reason to believe we were in a fire sale," he said.

Under the Pan Am-Air Florida proposal, Braniff would get the same $30 million that Eastern will pay for the routes. Pan Am would operate Braniff's routes to Colombia and Ecuador, including Panama-Colombia, and Air Florida would operate Braniff's routes between the United States and Panama, and all Braniff routes to Argentina, Bolivia, Brazil, Chile, Paraguay and Peru.