GLF-4 CREW DID NOT REMOVE THE OUTFLOW VALVE COVER BEFORE TKOF. THE CREW FABRICATED A STORY FOR LNDG AT THE NEAREST SUITABLE ARPT. THE CTLRS WERE CONCERNED THE ACFT WAS A SECURITY THREAT.

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CREW TOOK OFF WITH THE OUTFLOW VALVE COVER STILL INSTALLED OVER THE OUTFLOW VALVE. THE CAUSE WAS A DEV IN OUR NORMAL PREFLT DUTIES THAT WE NORMALLY ASSIGN TO EACH CREW MEMBER. I (CAPT) WAS TO SET UP THE COCKPIT; AND SIC WAS TO REMOVE COVERS (ENG AND OUTFLOW) AND DO THE EXTERIOR PREFLT WALKAROUND. THE SIC WAS BUSY CONVERSING WITH THE LINE CREW; SO I PULLED THE GEAR PINS; PUT THEM AWAY; AND RPTED MY ACTIONS TO THE SIC SO HE WOULD KNOW I HAD DONE THIS. I THEN WENT TO THE COCKPIT TO RESUME MY COCKPIT SET-UP. HE THEN REMOVED THE ENG COVERS AND DID THE WALKAROUND PREFLT. HE THOUGHT I REMOVED THE OUTFLOW COVER WHEN I REMOVED THE GEAR PINS; BUT DID NOT ASK ME. I ALSO FAILED TO CONFIRM WITH HIM THAT THE EXTERIOR PREFLT HAD BEEN ACCOMPLISHED. WE TOOK OFF AND REALIZED IMMEDIATELY WHAT WE HAD DONE. WE REQUESTED 10000 FT BE OUR LEVELOFF ALT UNTIL WE COULD DISCUSS THE PROB AND WHAT WE WANTED TO DO. BECAUSE OF EMBARRASSMENT; THE SIC SAID WE NEEDED TO LAND AT CHO ARPT TO DROP A PACKAGE THAT SHOULD HAVE BEEN LEFT AT THE IAD ARPT FBO. ATC THEN QUERIED AS TO WHAT THE PACKAGE CONTAINED (FOR SECURITY REASONS; I SUPPOSE). THE SIC THEN ADMITTED WHAT WE HAD DONE; AND THAT WE WANTED CLRNC TO LAND AT CHO; WHICH WAS APPROVED. ON LNDG; CHO TWR REQUESTED THE CREW CALL THEM FROM THE LCL FBO; WHICH THE SIC DID. THEY EXPLAINED THEIR CONCERN OF SECURITY; AND THAT THEY ALMOST DISPATCHED A MIL ACFT TO CHK OUR SIT OUT. WE DID REMOVE THE COVER AT CHO; REFILED AND CONTINUED WITH NO PROBS. THE MAIN CAUSE; WE DISCUSSED; WAS A DEV FROM NORMAL DUTIES ASSIGNED TO EACH CREW MEMBER; AND FAILURE TO CONFIRM WITH EACH OTHER THAT EACH CREW MEMBER'S DUTIES HAD BEEN COMPLETED. POSTFLT; WE DISCUSSED ADHERENCE TO ASSIGNED DUTIES; AND METHOD TO ASSURE EACH OTHER'S DUTIES HAD BEEN ACCOMPLISHED.