A U33F package from Evans Design contains (5) 3mm flashing red LED's that operate at 7-19v AC. The rectifier circuit is built into each prewired LED assembly. Pretty convenient solution for about $3.00 per light. Probably a few more tall locations around the layout where the other 4 could alert the low-flying planes....and houseflies!.
FWIW, of couseā¦.
KD