Two Russian-build MIG-21 Cuban fighter planes buzzed a US Coast Guard search helicopter in an act US officials called "extremely dangerous harassment." At the request of the Bahamas government, the US helicopter was searching waters off Cuba Monday for crew members from a Bahamian patrol boat sunk by Cuban MIGs last weekend. The incident occurred about 40 miles north of Cuba. Lt. David Kunkel, commanding the helicopter, said he had been warned of the MIG's approach by the Navy guided-missile destroyer Charles F. Adams, about 35 miles away. A few seconds later, he said the MIGs made three passes at his helicopter, coming as close as 50 feet.