Yes, most of the avionics systems on airliners have at least one
backup if they serve a critical function. Some have more.

Autoland is a triple redundant system and all three boxes have to
agree in order to autoland the airplane. Nav/Com radios are also
triple redundant on the 777. The Air Data Intertial Reference Unit on
the 777 (ADIRU) is fault-tolerant, and it is backup up by the SAARU.
TCAS is also redundant on the 777. Faults are detectable by BITE
software.

Dean

"Tom Sixkiller" wrote in message ...
"Dean Wilkinson" wrote in message
m...
Well, first of all this was a center controller, not a tower
controller. I don't believe that center controllers work alone in the
U.S., if they do I would be surprised. Secondly, their phone system
was offline and their conflict warning system was down... what, no
money for backup systems? Would that happen in the U.S.? I sure hope
not...

Do the airlines have redundant (backup) systems?