Serjio74/Getty Images Air traffic control (ATC) plays a vital role in making sure that planes, helicopters, and other aircraft don't get near each other. For example, the FAA recently ordered stricter air traffic control over routes where planes and helicopters intersect. In situations where aircraft must fly near each other, ATCs give directions to the pilots with the benefit of their powerful radar systems. That's all well and good if you're flying over land, but what happens if your flight takes you across the ocean? Radar coverage gives out after about 250 nautical miles. After that, you're on your own. To manage traffic where radar can't reach, aviation regulators have developed a system whereby tightly defined entry points, timings, and speeds can set a plane off on a kind of on-rails flightpath. Imagine trains leaving from the same station on the same tracks, at the same speed, and at different times. But this is the air, where even the most minor mistakes can compound into massive problems. The main concern, of course, is two planes crashing into each other. To prevent that, planes need to acquire special clearance for an ocean crossing on heavily used routes, like Europe to North America or, more recently, North America to Asia. This is done in air, about 40 minutes prior to breaking radar contact. At a minimum, the pilots need to provide the exact location of this oceanic entry point, the exact time they will hit it, and their flightpath. Math can go where radar can't reach Yalcin Sonat/Shutterstock Typically, ATC will respond to a clearance request with a mandated speed using what's called the Mach Number Technique. The plane must try to fly at this designated speed (say around Mach 0.8) for the whole time it is out of radar contact. This way, even though the plane is not being actively tracked, its position can be calculated. ATC can then use that information to issue clearances to other aircraft so as to avoid collision. This is why pilots must ensure they hit the oceanic entry point at exactly the right time: If that timing is off, all of the following calculations will be off, too, which could lead to a collision. Maintaining that speed is harder than it sounds. Winds shift, and pressures change. So, this isn't as simple as dialing in a number and going to sleep — pilots will need to carefully watch airspeed to make sure it's at the correct number. Even minor deviations can add up over time, putting the plane way off its calculated position. In a worst case scenario, that could mean that two planes that were calculated to stay apart instead crash into each other. Airborne railroad Naypong/Getty Images As mentioned above, in heavily trafficked areas, the aviation sector has developed a kind of on-rails model to simplify this. Called the Organised Track System (OTS, or PACOTS for the Pacific), this creates a specified flightpath that planes can follow. That makes it easy for ATC to keep aircraft longitudinally separated (i.e., leave plenty of space before and behind them). Just have your plane enter at the OTS point and on that exact path, and all ATC has to do is give you a safe speed. Because of changing atmospheric conditions and winds, these flightpaths are redrawn every single day. OTS isn't mandatory, however. Your transatlantic route may take you to less trafficked areas, like southern Africa, for instance. If for whatever reason you elect not to use an OTS path, that's fine, but clearance is a little bit more involved, since ATC has to do more elaborate calculations. Perhaps the answer to the air is in space Buradaki/Getty Images This is a slick system, but it has its drawbacks. The calculations and clearances create a lot of busywork for air traffic controllers that are already barely holding it together. Once you're over the ocean on your flightpath, you cannot deviate from it, whether or not you're using OTS. Pilots may wish to reduce or increase speed in order to optimize fuel use, but they can't do that with a mandated Mach number. They can get a new Mach number mid-flight, but this requires requesting a whole new clearance. And of course, the absence of any tracking can lead to horrifying situations like the disappearance of Malaysia Airlines Flight 370. The answer to being high over the ocean may be even higher over the ocean. Ever-increasing satellite coverage may soon give us a world where flights are never entirely out of tracking. Specifically, planes equipped with an ADS-B system (the same flight tracking that Congress would like to mandate for all Army helicopters after a crash in January 2025) may be able to use it with satellites. That's not quite the same thing as radar, but it would update the plane's position to ATC every second. Pretty good! If that pans out, then pilots could receive direct instructions from ATC over the ocean just like they would over land, so they'd be much freer to fly as they saw fit.