Update statement errors, parenthesis, failed validation ORACLE
Editor, that higlights matching braces should do the trick.
There are just too many of them. And... You left out the default values in outer nvl() or nvl keyword itself?

...
NVL(
 "nvl here?"(
  (SELECT F.FLI_PRICE FROM FLIGHT F WHERE F.FLI_ID = R.IN_FLIGHT_ID), 0
 )
 * NVL(R.IN_FLIGHT_SEATS_NO,0)
",default value here?") + ...


Go, have a break. This happens to me very often :-)