Mayor Jane Byrne, who flirted with an endorsement of President Carter last fall only to end up jilting him in favor of Sen. Edward M. Kennedy (D-MASS.), was coaxed back into the Carter fold today with help of more than $100 million in federal largesse.

Byrne, one of Kennedy's strongest supporters during his primary challenge to Carter, showed up at Chicago's Midway Airport this afternoon to welcome Vice President Mondale for a series of campaign appearances in the Chicago area.

The mayor followed up that initial signal of a new change of heart by introducing Mondale tonight at the Illinois Democratic Convention.

However, it appeared that it was more than the chance to offer Mondale the city's hospitality that moved Byrne away from her bitter opposition to Carter. Specifically, the vice president was preceded here by a number of announcements of federal aid clearly meant to smooth his way.

Last week, for example, Commerce Secretary Philip Klutnick was in town and on the same day city officials announced that they had received a $1 million grant from Klutznick's department for a new program.

Last Friday, the day Byrne returned to Chicago from a trip to Europe, officials here learned of a $13.2 million federal loan to the financially troubled Chicago Housing Authority. The city learned the same day of the final approval of the transfer of a parcel of federal land to Chicago that will allow construction of a new international terminal at O'Hare Airport.

The president last fall had all but commtted the administration to approving the land transfer at a polictical dinner at which Byrne all but endorsed him for renomination. But shortly thereafter, Byrne changed her mind and endorsed Kennedy, and until last week nothing more was heard of the land transfer.

Transportation Secretary Neil E. Goldschmidt was amonth those most outraged by Byrne's abrupt change of allegiance. He publicly suggested at the time that the city might suffer in terms of federal aid because of the mayor's switch.

Goldschmidt was here on Monday denying that what the federal government withholds for political purposes it might also provide for the same reasons. "I will not fly over Chicago dropping money for this election." he told the editors of the Chicago Sun-Times.

Today, however, the Sun-Times reported word from Rep. Dan Rostenkowski (D-Ill.) of $91.8 million in federal transportation grants to the city.

The Carter strategy here is to gain the benefit of the local Democratic organization by courting Byrne without alienating the anti-Byrne forces that joined with the president to defeat Kennedy in Chicago and throughout Illinois in the primary.

The strategy sometimes calls for a delicat balancing act. For example, Byrne is still feuding with state Sen. Richard M. Daley. Young Daley, the Democratic candidate for Cook County state's attorney backed Carter in the Illinois primary, and to show that the Carter campaign does not forget its friends Mondale's first stop here was at a Daley rally in surburban Blue Island.

The mayor was left at the airport. Carter campaign operatives here clearly also do not want to be associated too closely with Byrne. Many of them believe Bryne, then embroiled in a series of local controversies, ended up hurting Kennedy during the primary and they are not anxious for a repetition of that in November.

"We don't want her with her arm around Jimmy Carter," said the president's Illinois campaign coordinator, Michael Casey. "What we want is her people and for her to tell her people to work for Jimmy Carter."