Former US Air Force pilot John Venable called the Russian S-400 Triumph a serious threat and the world's leading anti-aircraft missile system, Defense News reports.
"It's the deadliest, it has the longest range, you'll have the hardest time hacking the system once it's got you," he said.
Flying at low altitudes is one of the few ways that pilots of aircraft like the MiG-29 can avoid an air defense system like the S-400 Triumph, he says.
