The most common Pre-Arm safety check that you may run into is not achieving GPS fix. This commonly happens when you attempt to arm the motors indoors, near tall structures, mountainous regions or due to sky blockage. In other words, preventing the GPS signal to reach the GPS module. Another thing to take note of is that in a new area, the IRIS+ can take anywhere from 5 to 17 minutes to achieve GPS lock, however once you’re locked on to enough satellites and have a low enough HDOP value ( dilution of precision, needs to be under 2.0 ) subsequent flights sessions will take less time to overcome this safety check.