Concorde's high cruising altitude meant people onboard received almost twice the flux of extraterrestrial ionising radiation as those travelling on a conventional long-haul flight.[127][128] Upon Concorde's introduction, it was speculated that this exposure during supersonic travels would increase the likelihood of skin cancer.[129] Due to the proportionally reduced flight time, the overall equivalent dose would normally be less than a conventional flight over the same distance.[130] Unusual solar activity might lead to an increase in incident radiation.[131] To prevent incidents of excessive radiation exposure, the flight deck had a radiometer and an instrument to measure the rate of increase or decrease of radiation.[128] If the radiation level became too high, Concorde would descend below 47,000 feet (14,000 m).