Tucson's Ryan Airfield and three other small Arizona airports remain on a list of small airports that face closure of their contractor-operated air-traffic control towers April 7, as part of automatic federal budget cuts expected to start kicking in next week.

And though aviation officials say the cuts will jeopardize air safety, the closures look more likely after efforts in Congress to keep the towers open failed this week.

The Federal Aviation Administration on Friday sent email updates to small airports, saying that two dozen of the 189 contract towers targeted for closure have been dropped from the list.

Ryan, located west of Tucson on West Ajo Highway, and three other Arizona airports - Glendale Municipal Airport, Phoenix Goodyear Airport and Laughlin-Bullhead International Airport - remain on the planned closure list.

Under the FAA's original plan to deal with the automatic cuts known as sequestration, contract towers at 173 small airports would close April 7, while 16 others would close by year's end.

On Friday, the FAA said towers at 24 airports that had appealed their possible closures will remain open "because closing them would have a negative impact on the national interest." Airports had been allowed to file arguments showing their tower operations were in the national interest.

The Tucson Airport Authority, which runs Ryan as well as Tucson International Airport, had petitioned the FAA to keep the Ryan tower open. On Friday, the authority issued a statement thanking Arizona's congressional delegation and local officials for supporting its appeal, and noting that flight operations will continue at Ryan without the tower.

"We are disappointed in this decision, given the significant safety and economic benefits the tower contributes to our community and Southern Arizona," the Airport Authority said.

A bipartisan amendment pushed this week by Sen. Jerry Moran, R-Kan., would have forestalled the closures by shifting $50 million in FAA research funding to the contract-tower program. But a vote on that amendment was blocked, so it wasn't included in a stopgap spending measure passed by Congress and signed by President Obama on Thursday.

Without a tower, pilots will have to coordinate takeoffs and landings themselves via radio and visual contact, as they do now at Ryan at night when the tower isn't open.

The Tucson Airport Authority said pilots flying in and out of Ryan can use UNICOM, a communications frequency used at uncontrolled (non-towered) airports for weather and navigational information.

The airport's Instrument Landing System (ILS), Distance Measuring Equipment system, and runway-end identifier lights will remain available, and the airport will continue to maintain them, the authority said.

Contact Assistant Business Editor David Wichner at dwichner@azstarnet.com or 573-4181.