Looking drawn and tired but seeming in good spirits, a 33-year-old American pilot was reunited with his fiance and family at Andrews Air Force Base last night after his release by the government of Angola in what was described as a goodwill gesture toward the United States.

Joseph Longo had been imprisoned in the southern African nation since he was forced to a crash landing by Angolan fighter planes in April. He arrived here in an Air Force jet after a 15-hour flight from the Angolan capital, where his release was secured Sunday by a four-member congressional delegation.

After descending from the C135, the diminutive professional pilot, dressed in freshly pressed khakis and a blue shirt, wrapped his fiance, Leslie Premick, in a long embrace, then hugged each of his three sisters and greeted his father where they waited on the Tarmac.

"I'm no statesman," said Longo, who spoke briefly at an impromptu news conference and seemed bewildered by the array of reporters and dignitaries who turned out for his arrival. "I'm just a driver of airplanes."

Longo had reportedly been trying to deliver a single-engine Beechcraft Bonanza to a customer in South Africa when he was forced down and detained on suspicion of spying for that country. The flight originated in Latrobe, Pa., according to one of his sisters, and it included a refueling stop in the Ivory Coast.

Longo, who planned to return to his home in Greensburg, Pa., declined to answer questions about how his airplane strayed into Angolan airspace and about the conditions of his 10-week imprisonment, saying, "It's been a long flight."

Rep. Howard E. Wolpe (D-Mich.), who heads the House Foreign Affairs subcommittee on Africa and who led the delegation, said last night that Angolan officials released Longo "as a symbol of their desire for more normal relations" with the United States.

The United States does not maintain diplomatic relations with Angola, a former Portuguese colony whose one-party Marxist government is backed by the Soviet Union and Cuba. The Reagan administration and South Africa are backing the prowestern Union for the Total Liberation of Angola (UNITA) under the leadership of Jonas Savimbi.

Despite its support for UNITA, the United States remains Angola's largest trading partner because of substantial operations by American oil companies there. Angolan officials have frequently proclaimed their desire for more American investment and the restoration of diplomatic ties.

Wolpe said the delegation "came away with the feeling that the U.S. and Angola have many interests in common." He told Longo, "There may be some lasting benefit from the misfortune you have suffered."

The delegation included Reps. Mickey Leland (D-Tex.), John P. Murtha (D-Pa.) and Nick J. Rahall (D-W.Va.)

Longo was greeted at Andrews by Sens. Arlen Specter and John Heinz, Pennsylvania Republicans who were active in trying to secure the pilot's release. Heinz said the cooperation of the Angolan government "does suggest that it it possible for this country and Angola to have meaningful discussions."

He added, "If this is an opening, so be it."