Despite the FA headline, 'mechanical difficulties' is in fact NOT in an acts of God list. Rather, they added it to their list of 'Force Majeure' events, along with 'acts of God.' From their Contract of Carriage:
Force Majeure Event means any event outside of Carrier’s control, including, without limitation, acts of God, meteorological events, such as storms, rain, wind, fire, fog, flooding, earthquakes, haze, volcanic eruption or any other event, including, without limitation, government action, disturbances or potentially volatile international conditions, civil commotions, riots, embargoes, wars, or hostilities, whether actual, threatened, or reported, strikes, work stoppage, slowdown, lockout or any other labor related dispute involving or affecting Carrier’s service, mechanical difficulties, Air Traffic Control, the inability to obtain fuel, labor or landing facilities for the flight in question or any fact not reasonably foreseen, anticipated or predicted by Carrier.
Likewise, the body of the FA correctly states that both mechanical difficulties and acts of God are in the same list. Of course, that doesn't make for such an eye-grabbing headline...