The hypersonic airliner Fireflash 3 takes off from London International Airport as per usual, but later sends out a mayday, reporting losing height rapidly and reporting their position as TS757/AR436. London Airport sends out the Air Sea Rescue squad who fail to find any trace of the craft at its last reported position. The crash makes headlines, and the Air Ministry has the entire Fireflash fleet grounded until further notice. Meanwhile in Thunderbird 5, Alan Tracy realizes that Fireflash 3's last reported position was incorrect, more than 50 miles out, explaining the inability to