A 700-mile aerial drug chase that involved three airplanes and stretched from the tip of Florida to Tennessee ended yesterday with a wild shootout on a runway and the confiscation of $500,000 in marijuana.

The five smugglers escaped after trying to run down pursuing federal agents with a truck on an airstrip.

Customs Service Agent Ramond Perez said a suspicious plane was first picked up on military radar about 75 miles south of Key West. Customs Service agents in Tampa sent a plane to follow it after vain attempts to contact the plane's pilot.

The first chase plane could not keep up, and a second chase plane was sent up from Jacksonville.

The smugglers' plane rolled to a stop about 3:30 a.m. at the Monroe County Airport and the customs plane from Jacksonville landed behind it moments later, crashing into a car that investigators said apparently had been strategically placed on the runway by the smugglers.

Two federal agents, armed with a .30-cal. rifle and a shotgun, leaped out of the crashed aircraft and ran toward the suspects, who were unloading the marijuana into a pickup truck, Perez said.

The men stopped loading the pot, jumped into the truck and drove down the runway, blazing away with guns and trying to run over the customs agents, he said. The agents were not hit, and it was not known if any of the smugglers were wounded.

"We got 41 bales of the wacky-weed," Monroe County Deputy Sheriff Don Sherlin said."

On Wednesday evening, a customs air patrol turned back a Cessna 404 attempting to land in central Florida and chased it to the Bahamaian island of Bimini where, short of fuel, it was forced to land. Inside the plane, authorities found cocaine with a street value of $130 million.

The two actions followed the largest cocaine bust in history Tuesday when Miami-based customs and Drug Enforcement Administration agents seized cocaine valued on the street at $950 million from a cargo jet at Miami International Airport.

No arrests have been made in any of the incidents, said a customs spokesman.