The move is the latest in a series of temporary groundings of type-fleets by US airlines in recent weeks following a US FAA review of compliance with airworthiness directives in the wake of the discovery of anomalies at Southwest Airlines.
In a statement United says: “As part of a regular review of maintenance records the company discovered that the functional test that checks the firing system on one of the five bottles in the cargo fire suppression system on the Boeing 777 was not performed and this was voluntarily disclosed to the FAA.
“United is in the process of checking this part of the system. This system is regularly tested as part of the pre-flight safety checks.
“These checks are related to compliance. United will not operate these aircraft until the tests are complete.”
The airline says it has 52 777s in its fleet.
At least some flights from London, Paris and Frankfurt to the USA have already been cancelled but the full extent of the disruption and how long it would last was not immediately clear.
Source: flightglobal.com's sister premium news site Air Transport Intelligence news