The military calls it “Whiskey 470,” a roughly 200-rectangular-mile patch of airspace over the Gulf of Mexico about 30 miles northwest of Tampa. It's a busy place where pilots learn how to fly one of the newest and most sophisticated fighters in the Air Force inventory.
Few people outside of military and aviation circles have heard about Whiskey 470. But last week, folks as far inland as Gainesville began reporting loud booming noises likely emanating from it.
“People are saying that their houses are shaking and windows rattling,” according to a post on the Citrus County sheriff's website.
The noises were tied to military exercises run out of Tyndall Air Force Base in Panama City that were taking place in airspace over the Gulf, said Aaron Gallaher, spokesman for the state's Division of Emergency Management.
“The atmospheric conditions were right so that the sound carried very far inland,” said Gallaher. “It was a freak occurrence.”
Still, the division put out a notice last week warning the public that the exercises will continue through the end of this week and that 34 Florida counties could be affected by noise, including Hillsborough, Pinellas, Pasco, Polk, Hernando and Citrus.
Whiskey 470 is part of a much larger area called the Gulf of Mexico Complex, stretching to about 20 miles east of the Louisiana coastline. Like much of the U.S., Florida is surrounded by restricted airspace. South of Whiskey 470 is Whiskey 168, from just south of Tampa to around the Florida Keys. The Federal Aviation Administration considers these “warning areas,” where the military trains and civilian aircraft can enter only after coordinating with the military.
A lot of coordination is required for these areas. The FAA controls the airspace in warning areas, and civilian aircraft fly through the areas on direct routes when the airspace is not in use by the military, according to the FAA, which has formal agreements with Pentagon over airspace use. While military use of some warning areas is scheduled in advance, sometimes it is on short notice.
The agreement between the FAA and the Pentagon allows the FAA to resume using the airspace when it cannot re-route flights around the warning areas due to severe weather. And there is also the Holiday Airspace Release Program, allowing commercial flights to transit special use airspace to give airlines a more efficient routing during busy travel periods, according to the FAA.
The Gulf complex is hopping these days, said Herman Bell, Tyndall's spokesman.
Tyndall is home to the 43rd Fighter Squadron, the nation's only F-22 Raptor training unit, and pilots routinely fly through the warning area practicing aerial combat, he said.
“Not only do pilots learn how to fly the F-22, they learn how to fight it too in that airspace,” said Bell, adding that the pilots take on other manned aircraft as well as remotely piloted F-4 Phantoms.
There is also a major training exercise taking place in Whiskey 151, to the west of Whiskey 470, said Bell, Called a Weapons Systems Evaluation Program, the exercise involves about 30 jets from various bases in the region, including F-15 Eagles and F-16 Falcons as well as the Raptors. During the exercise, which takes place about 150 miles off the coast, jets fire air-to-air missiles at small jet-powered drones called Firebees and the remotely piloted Phantoms for target practice. The exercise is scheduled to run through Friday.
In 2013, there were 10 such exercises, called WSEPs in military parlance. More than 330 air-to-air missiles were fired in total during those exercises, Bell said. The current exercise is the 12th this year but no finally tally has yet been made of how many missiles have been fired in 2014.
Given the timing of the calls about the booms, Bell said the most likely cause was noise produced by the Raptors, which can fly up to 1,500 mph, or about twice the speed of sound. Shock waves are created in front of an aircraft traveling at the speed of sound, or about 750 mph, and sonic booms are created when aircraft fly faster than the speed of sound, and break through the shock waves.
But the booms could also have been caused by the Eagles, with a top speed of 1,875 mph or Falcons, with a top speed of 1,345 mph, engaging with the Raptors during dog fights in Whiskey 470, or while on the way to their training mission in Whiskey 151, said Bell.
The noise complaints, which caused sheriff's offices in Hernando, Citrus and Gilchrist counties to get calls from concerned citizens, are unprecedented, said Bell.
“This is the first time we had many people talking about the booms,” said Bell. “We do (the exercises) all the time.”