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June 6 (Reuters) - Macquarie Infrastructure Corp is close to selling its Atlantic Aviation private aviation services network to KKR & Co Inc for around $4.5 billion, a source familiar with the matter said, as U.S. business jet flights surge.

A deal for Atlantic, the second-largest fixed-base operator network, has not yet been signed, the source said.

Fixed-base operators, or FBOs, a niche, fragmented sector that provides services ranging from hangars to fueling, have been drawing investor interest as private jet traffic rebounds in the United States.

Macquarie Infrastructure and KKR both declined comment on Sunday.

Macquarie has previously said it was seeking buyers for Atlantic Aviation for a deal by year’s end.

Earlier this year, Gatwick Airport owner Global Infrastructure Partners joined forces with Blackstone and Bill Gates' investment vehicle to make a $4.73 billion offer for Signature Aviation, the largest private jet services firm.

Business aviation flights in the United States, the largest market for corporate aircraft, surpassed 2019 traffic in May, according to recent data from FlightAware.

While business jet orders and deliveries dropped in 2020 due to the pandemic, private flights, which carry smaller groups and promise wealthy passengers less risk of exposure to the coronavirus, have generally fared better than airlines.

But some analysts question whether business jet charters will continue to lure new travelers, as vaccinated passengers drive a rebound in U.S. domestic commercial flights. (Reporting By Allison Lampert in Montreal and Chibuike Oguh in New York; Editing by Himani Sarkar and Stephen Coates )