Why a wait exists at all
Nitrogen absorbed during a dive leaves the body over time. Going to cabin altitude before that process has gone far enough increases decompression stress. The wait is a surface interval before flying, not a score to beat.
Published recreational guidance
Divers Alert Network summarizes consensus guidance for recreational divers who do not have symptoms of decompression sickness and who will fly at typical cabin altitudes. A single no-decompression dive has a minimum suggested preflight surface interval of 12 hours. Multiple dives in a day, or multiple days of diving, have a minimum suggested interval of 18 hours. For dives that required decompression stops, DAN notes that evidence is limited and a wait substantially longer than 18 hours appears prudent.
These are minimums, not targets. Longer surface intervals further reduce risk. Follow your training agency, dive operator, dive computer, and any aviation or medical instruction that applies to the trip. The DAN overview is at https://dan.org/health-medicine/health-resources/diseases-conditions/flying-after-diving/.
What DiveAtlas actually shows
After you log a dive, the No-Fly Timer in Diver Utilities counts down from that logged profile. The app uses 18 hours when the logged dive is a non-decompression dive and 24 hours when the logged dive is a decompression dive, then shows when that interval is complete.
That countdown is in-app guidance from the record you entered. It does not read a dive computer in real time, does not diagnose symptoms, and does not replace operator briefings or DAN-style published minima when those are more conservative for your trip.
Use the longer of the relevant waits
If your computer, operator, or published guidance asks for a longer wait than the app countdown, use the longer wait. If you have symptoms consistent with decompression sickness, do not fly; seek medical evaluation before travel.