You might mean April 1989. The "real" Pan Am ceased operations in December 1991 as WHBM says. If you do mean April 1999, your friend definitely did not fly Pan Am into the US. There's a "fake" Pan Am using the old name flying charters and limited domestic service today, but not in the Caribbean.

There are plenty of timetable and old OAG collectors who should be able to help you out. Perhaps a travel agent in your area stacks up old OAGs from years past. I have a handful of old Pan Am timetables from that era at home; I'll check tonight and see if the April 1989 schedule is among them.

Meanwhile, if you can reconfirm the date and/or airline, you might try posting your query to www.airliners.net, where a lot of timetable hounds hang out.