Air traffic control towers at Tucson's Ryan Field and three other Arizona airports will close next month because of the federal budget cuts, the Federal Aviation Administration announced Friday.

Ryan Field, off of Ajo Highway southwest of Tucson, is used mostly by owners of small, private planes.

Also closing will be the towers at Glendale Municipal Airport, Phoenix Goodyear Airport and Laughlin/Bullhead City Airport.

They are among 149 towers that will be closed in a four-week phased operation starting April 7, the FAA said in a press release.

The FAA must find savings of $637 million under the sequestration cuts that began March 1, the press release said.