There is an MEL - Minimum Equipment List and a CDL - Configuration Deviation List for each type of A/C, it provides specific information on what part/parts the A/C is allowed to fly without.
The flap track fairing you see missing comes under the CDL, it would have a restriction that it must be replaced within 'X' amount of days and while flying without it you must apply various performance penalties including an increase in fuel burn, in this case to the increased drag.
SMOC
Last edited by SMOC; 2nd February 2009 at 11:53.