According to Honeywell, tests during installation of a Wi-Fi system in an airliner found that LCDs in the airplane experienced a “momentary blanking… when exposed to higher-than-normal levels of electrical interference. STC [supplemental type certificate] testing is conducted before aircraft are certified to fly. There are no instances of a Honeywell screen blanking in flight. The screens have only blanked during a ground test and under conditions that will not be experienced in flight. At regular power levels, the displays have functioned normally and Boeing and Honeywell have concluded that normal operation of an installed Wi-Fi system will not cause any blanking of a Phase 3 display. This is not a safety issue with 737s or 777s currently in service.” Boeing has deferred activating the Wi-Fi system in aircraft with Phase 3 displays, according to Honeywell, “and has not delivered any installations that would have this issue.”