(CNN) -- It's summer and vacation planning is in full swing. While dreaming of sun and sand or mountains and lakes, many travelers forget that flying carries some uncertainties.
That's where air traffic control comes in. And today the Federal Aviation Administration is celebrating 75 years since 15 federal workers started operating in three control centers in 1936.
The first control centers were in Chicago, Cleveland and Newark, New Jersey. Now there are more than 300 federal air traffic control facilities and more than 15,000 controllers.
"As a pilot, I am in awe of the aviation safety and technological advancements that have been made in the last 75 years," said FAA Administrator Randy Babbitt. A sweeping overhaul of the air traffic system, called NextGen, will make aviation even safer and more efficient, Babbitt said. The system will transition from using ground-based radars to satellite technology
The anniversary comes at a time of year when severe weather can make getting to any destination a challenge. It's thunderstorms that ramp up the business of air traffic control, Babbitt told CNN.
Babbitt, the FAA's 16th administrator and a veteran pilot, is no stranger to dealing with air traffic in bad weather. Standing in the middle of the operations at the Air Traffic Control System Command Center in Northern Virginia, he explained how today's controllers plan air traffic for the entire country, taking into consideration how weather and other events will affect traffic patterns.
"The beauty that we have here is the ability for us all to see it and view all the information together. So everyone who has an interest in the solution, you know, what are we going to do with the traffic, has situational awareness. How we are going to reroute traffic? It all comes together here," Babbitt said.
When the system started in 1936, the fastest plane in the commercial fleet was the Douglas DC-3. A coast-to-coast flight lasted about 17 hours in this aircraft, which carried 21 passengers. Today, jets carry hundreds of passengers on each flight from New York to Los Angeles in about five hours.
About 50,000 aircraft are in U.S. airspace each day, carrying about 1.7 million passengers.
The command center in northern Virginia is staffed round the clock with controllers balancing traffic demand with system capacity. Specialists work with others in the aviation industry to minimize flight delays and congestion and maximize the overall use of the airspace.
"They can see the overall traffic issues. They can see what's happening to traffic and take early action to reroute people and minimize delays," Babbitt said.
Most controllers don't actually see the aircraft they are managing, but instead monitor radar screens at locations throughout the country. Controllers link up with flight crews by radio once their planes are airborne. They are responsible for aircraft in between airports and use sophisticated tracking systems to maintain a safe distance between planes.
The summer travel season can be more challenging because of unpredictable weather, said Terry Biggio, an FAA air traffic manager at the Atlanta Air Route Traffic Center in Hampton, Georgia.
"Starting March 1, severe weather season will start. It will go until August and most of September. So you might get some gridlock at the airport. We actually take a look at this particular picture, this graphing, and help free up the gridlock. The coordination takes place here," Biggio said.
So if you are traveling this summer and you're sitting at the airport and it's a clear blue sky, you still may experience delays due to unforeseen weather in other parts of the country.
But on this 75th anniversary, just as every day, the job of air traffic control is to minimize troubles in the sky.