Primark Corp., a conglomerate based in McLean, yesterday reported a loss for 1987 because of a restructuring in its aviation services division. The restructuring, which produced a $53.2 million charge against earnings, resulted from the loss of a United Parcel Service contract under which the Primark division handled some of UPS's jet aircraft flight and maintenance operations.

Primark said it lost $1.7 million (9 cents a share) in 1987, compared with a profit of $53.8 million ($2.73) a year ago. Revenue fell to $1.4 billion, from $1.6 billion in 1986.

Primark said it lost $36.7 million in the fourth quarter, in part because of the loss of the UPS contract. In the fourth quarter of 1986, Primark had a $15.6 million (79 cents) profit. Revenue in the quarter fell to $370.9 million from $406.3 million a year ago.

Primark, which also owns Michigan Consolidated Gas Co., a large utility, and has interests in telecommunications and financial services, recently announced plans to spin off the utility as a separate company.

"Primark faced a number of challenges in 1987 that required management to focus and redefine our operations," Chairman Robert W. Stewart said in a statement yesterday.