Virgil remote-controls two elevator cars while driving a third to cushion the crash-landing of the Fireflash airliner. On the craft's second landing attempt, elevator car #1 suddenly breaks free and speeds off the runway and overturns. This scene came about because during filming one of the model cars indeed broke free and slid off the miniature runway. The special effects crew and Gerry Anderson both agreed that this "gaffe" would work in the context of the story, so Anderson wrote this setback to International Rescue into the plot.
This episode has no on-screen title but is referred to in all production documentation by the title of the shooting script as "Trapped In The Sky".
It is established that Jeff Tracy's servant, Kyrano is the half-brother of the villain The Hood who is able to get information from him telepathically. This was also used in Desperate Intruder (1965). Kyrano apparently has no memories of this or he surely would have revealed it to Jeff Tracy. Jeff never knew he had an unwitting traitor working for him.
According to the Gerry Anderson Story in Volume 5 of Gerry Anderson: The Vintage Comic Collection, inspiration for this episode came from Anderson's National Service at RAF Manston. Whilst up in the control tower, he watched a plane make an emergency landing with its undercarriage still retracted, and amazingly none of the crew were seriously injured despite the tricky landing.