The television relay tower (featured in the episode "Edge of Impact") is seen to be owned by British Telecommunications Ltd. The use of this company name in the series pre-dated the formation of the real-life British Telecommunications plc (or BT) by nearly twenty years.
Both Thunderbird One and Thunderbird Two are shown going through their pre launch process in silence, without the usual march music. This is to emphasise the subtlety of the launch procedure whilst there is a visitor on the island.
This is the second instance of where Alan's portrait is used to show radar of an aircraft approaching Tracy Island.
When Jeff is reading the news of the first Red Arrow crash, there is a box of Corn Flakes that has clearly been altered to say 'OOBN FLAKES.'
This is the only episode where the Hood appears but does not attempt to spy on International Rescue.