As for the BA flight they should have had working landing lights...
, how many of them should be working depends on the minimum equipment list supplied for that specific aircraft, and approved by the CAA in this case, in the US that would be approved by the FAA.
Bassically the reg's state that when an airplane is operated for hire, which BA obviously does, then it must have a working landing light, in order to land after dark..
(but if they fail in flight, sure enough you eventually have to land anyway, lights or no lights, no biggy plenty of lights on the runway.....
)
This should answer it all.....
gr.
InflightFeather