Why was my flight delayed and un-delayed twice?

Question

I was on DL2941 from MSP to ABQ on June 30, which was scheduled to depart at 6:35pm CDT. At 4:48pm, I got a text saying the flight was “now departing” delayed at 8:10pm; ten minutes later at 4:58, I got another text that the flight was “now departing” at 6:35pm, i.e., on time. Then, shortly before boarding, the gate agent announced the flight was delayed, I believe to 8:05 but I’m not sure; then a few minutes later he announced that it was on time, perhaps something about “the tower”.

My question: What happened to cause not only one but in fact two delay/un-delay cycles?

According to Flightrader24, the aircraft (N3747D) had arrived from SLC that morning at 11:21am, i.e., several hours before my flight. I had looked at this schedule the day before and I’m pretty sure it was the same.

I know crew scheduling is also a thing that causes delays, but I don’t know how to obtain any public data on that. I believe weather was good at MSP, ABQ, and along the route.

I’m most interested in “teach a person to fish” type answers, i.e., how could I have figured this out myself?

This question has some good discussion of the general issues in play, but I’m interested in the specific reason(s) for my flight.

Answer 1

Most non-weather delays are maintenance snags flagged by flight crews on the previous flight due to fault messages in the flight deck. These airplanes are so complex, and the components have such hard use with temperature and pressure extremes, things are breaking all the time (why there are two and three of the more important components).

The industry standard is one delay over 15 minutes, due to something in the airplane breaking or malfunctioning, in 100 departures, called Dispatch Reliability. Most mature airplanes achieve a DR between 98.5 and 99.5%. But one is a hundred is still quite a lot, and less reliable airplanes are more like 2 or 3 per 100.

The airplane comes in with a snag, and company Operations either have maintenance come to the gate to troubleshoot and fix, or unload the passengers and take the airplane somewhere to be worked on.

Maintenance will do troubleshooting and tell Operations how much time it's expected to take to fix based on standard man-hour estimates for maintenance tasks. Operations will set a new departure time.

Then the fix doesn't work, and they have to continue working on it with a new departure estimate. Then after that, it still doesn't work, and and they either keep plugging at it, or Operations decides to switch the airplane for a spare one (some operators keep spare aircraft to keep schedule completion rates as high as possible; at this point, many operators without access to spare airplanes will simply cancel the flight).

That may not be what happened in your case, but it's a typical scenario.

Answer 2

I didn't see anything obvious after a quick glance, but one "teach to fish" source for ATC delays is the FAA's National Airspace System Status site: https://nasstatus.faa.gov

More "under the hood" information can be found at the links at the top of the page, specifically the Advisories database at https://www.fly.faa.gov/adv/advAdvisoryForm.jsp. You can also check if your flight has an Expect Departure Clearance Time at https://www.fly.faa.gov/edct/jsp/edctLookUp.jsp. Remember to use the ICAO airline identifier, not the IATA identifier (DAL vs DL).