The Boeing 737 MAX 9 aircraft that were grounded after a door plug blew out will soon be allowed to take to the skies again, the US aviation regulator said on Wednesday. The Federal Aviation Administration (FAA) said it has approved “a thorough inspection and maintenance process that must be performed on each of the grounded 171 Boeing 737-9 MAX aircraft.” “Upon successful completion, the aircraft will be eligible to return to service, the authority said in a statement. According to the airlines concerned, such an inspection takes several hours per aircraft. On January 5, an almost new Boeing …