Passage: With the escalating situation in Southeast Asia, 28 B-52Fs were fitted with external racks for 24× 750 lb (340 kg) bombs under project South Bay in June 1964; an additional 46 aircraft received similar modifications under project Sun Bath. In March 1965, the United States commenced Operation Rolling Thunder. The first combat mission, Operation Arc Light, was flown by B-52Fs on 18 June 1965, when 30 bombers of the 9th and 441st Bombardment Squadrons struck a communist stronghold near the Bến Cát District in South Vietnam. The first wave of bombers arrived too early at a designated rendezvous point, and while maneuvering to maintain station, two B-52s collided, which resulted in the loss of both bombers and eight crewmen. The remaining bombers, minus one more that turned back due to mechanical problems, continued towards the target. Twenty-seven Stratofortresses dropped on a one-mile by two-mile target box from between 19,000 and 22,000 feet, a little more than 50% of the bombs fell within the target zone. The force returned to Andersen AFB except for one bomber with electrical problems that recovered to Clark AFB, the mission having lasted 13 hours. Post-strike assessment by teams of South Vietnamese troops with American advisors found evidence that the Viet Cong had departed from the area before the raid, and it was suspected that infiltration of the south's forces may have tipped off the north because of the South Vietnamese Army troops involved in the post-strike inspection.

Question: how many bombers were in the operation Arc Light?
30