Boingo Wireless of Los Angeles announced today that it would offer free Wi-Fi coverage at 35 U.S. airports to 40 million Android handsets on Sprint’s cellular network.

The multi-year partnership will boost data and voice connectivity for Sprint customers automatically as they come in range of Boingo’s airport Wi-Fi hotspots. Airports were chosen because they often are difficult places for cellular networks to provide coverage.

Among the airports covered through the partnership are Los Angeles International, John F. Kennedy International and Chicago’s O’Hare International Airport.

Boingo declined to disclose terms or length of the deal.

“Carrier offload as a concept, that’s something we’ve been talking about at Boingo for years,” said Boingo Chief Executive Dave Hagan. “Wi-Fi networks will become a lot like an add-on to cellular networks.”

Though Boingo has had agreements of this nature in the past with telecom companies, the Sprint deal represents the first time the integration happens automatically for a large number of cellular network customers.

Though the partnership only supports Android phone users, Hagan said they are testing for a possible later iPhone rollout.

Sprint has an option to further extend the partnership to Boingo’s other Wi-Fi hotspots in businesses and sporting venues.

Hagan said the partnership does not limit it from entering similar deals with other cellular network providers.

Technology reporter Garrett Reim can be reached at [email protected]. Follow him on Twitter @garrettreim for the latest in L.A. tech news.