Thirty House lawmakers signed a letter urging FAA to reverse course on its air traffic control charges for the Experimental Aircraft Association’s AirVenture in Oshkosh, Wis., stepping up the political pressure on the agency as the event was set to open July 29.

The bipartisan letter, which included the signatures of a number of House GA Caucus members, follows a similar letter sent by 28 senators in June. The House lawmakers told FAA Administrator Michael Huerta that they were “greatly concerned by the boldness of the FAA to assume that this type of revenue mining would be deemed acceptable and lawful,” and appealed to Huerta to reconsider the agency’s funding for AirVenture and other aviation events.

FAA in May informed EAA that it was charging for travel costs, per diem expenses and overtime pay for the federal controllers brought in during the weeklong AirVenture. The Oshkosh tower is usually run under the contract tower program, but FAA brings in nearly 80 controllers and supervisors to handle the 8,000-10,000 aircraft that fly into AirVenture. EAA expects this year’s event will be on track with past years, bringing in nearly one-half million attendees.

EAA acquiesced to the charge and signed an accompanying contract, but did so under protest and has since filed a petition with the U.S. Court of Appeals for the Seventh Circuit in Chicago seeking a refund of the nearly $450,000 in payments.

FAA, however, has showed no signs of backing down, with Huerta responding to the Senate letter that the agency has entered into reimbursable agreements for special aviation events since 2010. “We have been reimbursed for providing services for NASCAR events, the Super Bowl, the PGA tour and other sports events,” Huerta told the senators. “The services we provide for these events result in additional overtime costs, extended hours of operation at FAA facilities and, in some cases, the use of a temporary tower.”

He acknowledges FAA has funded the incremental costs associated with Oshkosh in the past, “but in this very difficult budgetary environment … a reimbursable agreement is particularly prudent now as we are trying to reduce travel costs across the agency.”