CHICAGO -- The planned shutdown of nearly 240 air traffic control towers nationwide under federal budget cuts will strip away an extra layer of safety during takeoffs and landings, leaving pilots to manage the most critical stages of flight on their own.The towers slated to close are at smaller airports with lighter traffic, and all pilots are trained to land without help by communicating among themselves on a common radio frequency. But airport directors and pilots say there is little doubt the removal of that second pair of eyes on the ground increases risk and will slow the progress that has made the U.S. air system the safest in the world.It's not just private pilots in small planes who stand to be affected. Many of the airports in question are served by major airlines, and the cuts could also leave towers unstaffed during overnight hours at some big-city airports such as Chicago's Midway and General Mitchell Airport in Milwaukee. The plans have prompted airlines to review whether the changes might pose problems for commercial service that could mean canceling or rescheduling flights.Without controllers, risk "goes up exponentially," said Mark Hanna, director of the Abraham Lincoln Capital Airport in Springfield, Ill., which could see its tower close.As part of the spending cuts that took effect this month, the Federal Aviation Administration is being forced to trim $637 million for the rest of the fiscal year that ends Sept. 30. The agency said it had no choice but to subject most of its 47,000 employees, including tower controllers, to periodic furloughs.Representatives of the FAA declined to discuss the effect of the cuts with The Associated Press. In two recent speeches and in testimony before Congress, Administrator Michael Huerta stressed that safety remains the FAA's top priority. But many in the aviation sector are frustrated that brinkmanship in Washington has affected such a sensitive area of aviation.In Dallas-Fort Worth, five contract control towers are on the proposed closure list, FAA spokesman J. Lynn Lunsford said: Fort Worth Spinks, Arlington Municipal, Grand Prairie Municipal, Dallas Executive and McKinney.The towers were selected because they record the fewest takeoffs and landings annually. FAA employees, including air traffic controllers, will begin taking furlough days in late April, he said. That will result in a 10 percent fewer controllers working on any given day at all airports, including DFW. Fewer controllers means they are able to handle fewer flights and air travelers will likely see delays, Lunsford said.A final list of which towers will close is expected Friday, he said.Jim Montman, manager of the Santa Fe Municipal Airport, which is on the list for tower closures, said the absence of controllers raises the risk of midair collisions "or some sort of incident where somebody lands on the wrong runway. ... That critical link is gone."The first round of closures is expected to target 173 towers run by third-party contractors, rather than FAA staff. That process could start early next month.Those airports had until Wednesday to argue for keeping their towers open, but few are considered likely to escape the cuts.Staff writer Sandra Baker contributed to this report.