If you’ve flown out of a major airport before, chances are that you might have noticed that your plane doesn’t tend to just fly in a straight line right after takeoff most of the time. Similarly, you might wonder why your flight continues to turn time and time again before you come in for a landing. And while there can be many reasons for such happenings, there are two things that dictate where you go and when you do it after takeoff and before landing: SIDs (Standard Instrument Departures) and STARs (Standard Terminal Arrival Routes).
Before I explain SIDs and STARs more in-depth, I have to explain what waypoints mean in the aeronautical sense. I’ll also say that I will not be covering low-altitude airways, high-altitude airways, VORs, or any other types of en-route navigation. Otherwise, I’d be here all night, so we’ll keep it to the basics of arrivals and departures, which are SIDs and STARs.
Waypoints, as you might imagine, are specific latitude and longitude coordinates that are plotted at particular locations on a map and given an identifier that consists of five characters — letters, digits, or a combination of both. They don’t have to be given gibberish names by any means; they can be pretty fun, in fact. For example, the Boston area has some pretty interesting waypoints like DRUNK, FENWY, LBSTA, LONER, and TEKKK. New York, meanwhile, has FIXIN, KIWIE, NAYIK, and QUENE. In fact, this site has a directory of a number of different waypoints, both in the U.S. and elsewhere, so go ahead and check them out if you’re so inclined.
A Standard Instrument Departure, known as SID for short, is a departure procedure designated by air traffic control for aircraft to follow. Usually, it consists of 4 to 5 different waypoints, followed by an aircraft’s GPS, and the SID is named after last waypoint in the sequence. Though the waypoints on the CELTK4 departure from Runway 33L are different than the waypoints on the same SID from Runway 09, the CELTK4 departure can be assigned regardless of the runway. Why? Well, each runway’s particular routing ends at the same waypoint, and that’s the important thing; as long as the pilots are clear on which waypoints they’re taking to get to CELTK, which will be plotted ahead of time, then you are good to go.
As you can see above, the CELTK4 departure chart has routes listed for the majority of Logan’s six runways. Taking off from Runway 4R, you’d fly through waypoints NHANT, HURBE, ORRR, and TONNI, most of which is over water. Taking off from Runway 33L, you’d fly through TEKKK, COUSY, CBEAR, and COLYN, which would take you over Massachusetts land. Regardless of which runway a given flight takes off of, it will still end up at waypoint CELTK off the coast of Massachusetts.
The CELTK4 departure is one of my favorites, as it’s generally used by transatlantic flights headed to Europe. In fact, when planes fly CELTK4 off of Runway 33L, I can sometimes see them from my bedroom as they turn to the southwest. As you can see below, a Boeing 747-400 operating as British Airways 214 flew that route recently, and the image below is a screenshot of the flight’s track in relation to the Greater Boston area.
How can you tell which SID your flight is using, and therefore where you’ll be flying? Well since a SID can exist for multiple different runways, you’ll probably need to know which runway you’re using in order to have a better idea. However, you can find out which SID you’re using by looking at the bottom right-hand corner of your given flight’s track on FlightAware.
While many SIDs simply end at the final waypoint, there are certain SIDs that have additional legs called “transitions,” which are comprised of waypoints, navaids, or VORs. The purpose is to “transition” the aircraft from the area around the airport to its proper flight course, and it makes it easier for air traffic control to get a plane to its proper flight course by having multiple transitions for different directions. Regardless, the SID’s purpose is clear: to make life simpler and safer for pilots and air traffic control.
Much like the aforementioned departure procedures, a Standard Terminal Arrival Route, known as STAR for short, consists of a number of different waypoints. Though logical in the end, STARs are a little bit more complicated than SIDs, in that there are more steps and they don’t lead you directly to the runway that you’ll be landing on.
For example, when arriving on the OOSHN3 arrival into Boston as many transatlantic flights do, a flight will go through a “transition,” which I’ll attempt to explain more thoroughly here. For example, the AJJAY transition consists of waypoints AJJAY, SUFFI, NIKKO, and EURRO. Then, once a plane passes over OOSHN, it will diverge onto more specific waypoints. For example, if it’s landing on Runway 22L, it will head to GRGIO, BRGIT, ADDDA, and LEEZI. However, it’s it’s landing Runway 04R, it will cross TTERI, WAATR, FLUTI, GRIFI, GGABE, and JOBEE to land on Runway 04R.
At the point which the plane hits its last waypoint in the STAR, air traffic control will vector it to its final approach course, whether that’s an ILS (Instrument Landing System) approach, an RNAV (GPS) approach, or, in rare cases, a visual approach. At that point, the pilots are now following vectors from air traffic control and whatever they’re using for landing, rather than following the STAR.
Similar to SIDs, FlightAware will often list a given flight’s STAR. Often times, it’s the last word written under the “Route” category, as displayed below.
How Are Pilots Assigned SIDs and STARs For Flights?
This is an intriguing question, and there’s no one correct answer. However, a lot of it simply has to do with what is the most geographically direct routing.
For example, flights going to Europe from the United States often follow the “North Atlantic tracks,” a series of routes that are designed to maximize the impact that the jetstream has (think tailwinds). If the tracks for a particular night are running from, say, Newfoundland to the northern part of Ireland, then an aircraft departing from Boston will probably use the LBSTA4 departure over the CELTK4 departure, as waypoint LBSTA is to the northeast of Logan Airport and more in line with the natural routing to Newfoundland. However, if the tracks are running a more southerly route, such as from Nova Scotia to the southern part of Ireland, then the same aircraft would probably use the CELTK4 departure because waypoint CELTK is further south, and thus more in line with the natural routing that the flight would take to get to the tracks that start around Nova Scotia.
Sometimes, there are other considerations to be made. Noise abatement procedures can have an impact on which departure a particular aircraft might fly, as one might be much more feasible than another. Another thing is that one particular SID might have a much more direct course for a given runway than another: a SID that ends northeast of a given airport would make much more sense for a pilot taking off to the northeast than if the same pilot was taking off to the southwest. Finally, some flights and airlines simply seem to have a preference for one particular SID over another: the Virgin Atlantic pilots flying out of Boston almost always use the LBSTA4 departure when departing Runway 33L, while the Swiss pilots almost always use the CELTK4 departure from the same runway. I’m probably missing some things here, but those are common reasons for choosing one SID or STAR over another.
It’s also worth mentioning that SIDs and STARs — particularly SIDs, in my observation — are subject to change due to any of those factors. I can’t tell you the number of times that I’ve checked FlightAware in the morning to see what particular SID a transatlantic flight will be using that night, only to have the information change hours before the flight. However, when all of the factors that go into choosing a SID are considered, it actually makes quite a bit of sense.
How Do I Figure Out Where a SID/STAR Involving a Particular Runway Goes?
The most important thing when figuring out SIDs, STARs, and their routing within the real world is to know where waypoints are on a map. If you see a waypoint listed on a SID or STAR that you don’t recognize, often times simply Googling will do the trick. For example, in writing this page, I wanted to know where waypoint JOBEE was, so I searched “JOBEE waypoint.” Sure enough, the map was the first result that showed up, and such a result should be fairly consistent across the board.
Another thing to recognize is that not all airports have published SIDs, at least in the way that I have explained them. At smaller airports, the published departure procedure may simply consist of the requirement that you fly the runway heading until given vectors, as illustrated below by the description for the departure route from Bangor International in Maine.
I fully recognize that not everyone will care about the particular routing that they’re taking. To many, simply getting from point A to point B successfully is all they’re looking for. However, if you want to figure out flight patterns over your neighborhood, workplace, or any other location, AirNav is an excellent resource with a number of different charts, diagrams, and maps for SIDs and STARs at many airports. By finding a chart that lists the waypoints for a given SID or STAR and a given runway, you’ll have the waypoints that you need to learn more.
Note: All of the charts, diagrams, and maps used here are displayed solely for informational purposes.