The consortium behind a formal offer for Manston Airport has gone public with details of its takeover bid, hours after the airport’s closure has been announced.

RiverOak Investment Corp LLC of Stamford, Connecticut, had a £5m formal offer for the site rejected by owner Ann Gloag yesterday.

Earlier today, it was announced the airport is to close on May 15, after the consultation on its closure failed to find a “viable alternative”.

However, the American group says it presented a long-term plan for the airport’s future, backed by the firm’s $350m of assets.

They also say they have a track record of this kind of takeover, having restructured a cargo airport in Texas.

Ann Gloag would not comment on the company's statement.

The firm says it is “distressed” to learn of the closure announcement but still willing to negotiate a takeover.

The company says its formal offer to acquire 100% of the shares in the company owning Manston Airport was “significantly higher” than the investment made by Ann Gloag since buying the airport in November.

The group visited Manston on April 29 and visited Ann Gloag and her advisor in Scotland on May 2.

The company says it has “a successful track record of turning around troubled operating and real estate assets”.

It claims it is a partner of a number of aviation operations, specialising in aircraft maintenance and cargo operations.

“RiverOak is distressed to learn of the announced closure of Manston today and remains willing to engage with all parties to achieve a solution” - Manston bidders

It continues: “Principal partners at RiverOak have extensive US experience with the capital markets and debt restructuring of a number of major airport assets, one of which is a singular maintenance and cargo hub in Texas.

“RiverOak has developed a long term plan to own and manage Manston as an airport in line with its investment philosophy of diversified investing in asset backed businesses.

“It remains committed to investing in and developing Manston as a successful diversified aviation services, cargo and potential future passenger airport facility, and values Manston as an important piece of aviation infrastructure that is very important to both Kent specifically and the United Kingdom in general.

“RiverOak is distressed to learn of the announced closure of Manston today and remains willing to engage with all parties to achieve a solution which allows the airport to continue operating and preserves the jobs of its staff.”

RiverOak's statement comes as union Unite condemned the decision not to take up the offer, saying members were "shocked and very angry".

In a statement released this afternoon, a union spokesman said: "We can't believe that the owners of Manston have rejected a viable offer to buy the airport, which would leave the owners in profit.

"We believe Manston should continue as a viable airport. It is vital to the local economy in terms of employment and economic growth in Kent."

It said the union had lodged a formal grievance with the owners over what it dubbed "a complete failure to consult with the unions over this bizarre decision."