If you build a system, you'll know its flaws. A common flaw with radar systems is them detecting something that's not a plane as a plane - e.g., the sun over th

If you build a system, you'll know its flaws. A common flaw with radar systems is them detecting something that's not a plane as a plane - e.g., the sun over the horizon. If he built the software that automatically rejects such mistaken identifications, he also knows in which situations you'll get a false positive reading, and can tell his friend the perfect timing for the prank.