"There is going to be a very thorough investigation," Lange said. "It's obviously a very tragic incident."
The NTSB said it's investigation could take up to a year.
Secretary of Defense Leon Panetta "was deeply saddened by news of the tragic accident involving veterans heroes and their spouses in Midland," Pentagon spokesman George Little said in a statement. "His thoughts and prayers are with the families of the victims, with those injured in this incident, and with the entire community."
Midland is about 320 miles west of Dallas.