Here's a question you can ask any corporate pilot, charter operator, or flight instructor and get an honest answer if they trust you. How many times in the last year did you bust a published restriction on a SID or STAR?
The honest answer is usually not zero. The honest answer is also usually not high. But it's a number, and the number is bigger than most pilots will admit publicly, and considerably bigger than the violation statistics suggest.
Procedure busts are common. They're also almost invisible. Understanding why is useful for understanding what the actual safety landscape looks like.
What "procedure bust" means
A SID, STAR, or instrument approach procedure has restrictions baked into it. Altitude crossings, speed limits, lateral path requirements. The procedure says you cross BIKKR at or above eight thousand, or at and below two hundred eighty knots, or in this configuration. These restrictions exist for a reason. Traffic separation, terrain clearance, noise abatement, airspace structure. ATC builds their workflow around the assumption that you're flying the procedure as published.
A bust is when you're not. You cross the fix five hundred feet low. You're indicating two ninety. You're two miles outside the corridor. Sometimes these are dramatic and obvious. Most of the time they're minor and recoverable, and the pilot doesn't even notice.
The FMS is supposed to handle most of this. Load the procedure, let the airplane fly it. This works fine until you get a vector around weather, or ATC gives you a non-standard altitude assignment, or the procedure you loaded isn't the variant that's actually been cleared, or the speed restriction is on a fix and the FMS is managing speed differently.
Why ATC doesn't say anything
ATC has the data. They see you cross the fix at the wrong altitude. They see your speed on the radar tape. They can run the numbers later if they want to.
What they almost never do is violate you for it.
The reason is operational. ATC's job is to keep airplanes apart and move traffic. Violating pilots for minor procedure busts that didn't actually create a separation problem isn't their priority. The threshold for action is usually higher than the threshold for a technical violation. If your bust didn't cause a problem, you probably won't hear about it.
This is a sensible operational stance. It's also why the data on procedure busts is essentially invisible. The events happen, ATC notes them, ATC moves on. There's no public record. Nobody knows the rate. The pilot often doesn't know they busted anything at all.
The ASRS window
The one place this data shows up is in voluntary reports. NASA's ASRS database receives a steady stream of pilot-submitted reports about procedure deviations. These are the cases where the pilot recognized what happened, decided to file, and wrote it up to protect themselves from enforcement and contribute to the database.
What you can learn from ASRS is that procedure busts happen across operator types, aircraft categories, and airspace complexities. They happen to airline crews and Part 91 owners. They happen on familiar procedures and unfamiliar ones. The most common contributing factors are workload, automation confusion, and unexpected ATC instructions that conflict with the loaded procedure.
What you can't learn from ASRS is how common busts actually are, because the database only captures voluntary reports. The denominator is unknown. The reports that exist are the visible portion of a much larger iceberg.
Where this matters
If you operate aircraft, this is the kind of data you should want. Not for enforcement, but for training. Knowing that your operation busted a procedure restriction six times last quarter, on three specific procedures, tells you something useful. It tells you where the training gap is, where the procedure complexity is, where the workload spikes happen.
Flight data monitoring systems can produce this data automatically. The signals are all there in what your aircraft already records. ADS-B has your position. Your altimeter has your altitude. Your airspeed indicator has your airspeed. Compare these to the published procedure and you have your answer.
The first time you run this analysis on your own fleet, the number is going to be higher than you expect. That's normal. That's the whole point of measuring it. The number that matters is what it is twelve months from now, after you've fed the data back into your training.
What ATC won't tell you, your own systems will, if you set them up to.