October 1, 1958 saw the beginning of the unit's commitment to five-minute runway alert, a task that would last for 38 years. The arrival of the F-102 Delta Dagger in 1966 ushered in the supersonic age.

In 1972, the unit was re-designated the 120th Fighter-Interceptor Group and assigned the F-106 Delta Dart. It was the first Air National Guard unit to operate the Delta Dart, the 186th FIS/120th FIG received its first two F-106A's (57-2485 and 57-2487) on 3 April 1912. The squadron was located at the Great Falls airport. The initial batch of 21 F-106's consisted of one F-106A from the 319th FIS, one F-106A and one F-106B from the ADWC, and 17 F-106A's and one F-106B from the 460th FIS. The 186th FIS did well in William Tell weapons meets: first place in 1974, first in 1976, second in 1978, and second in 1982' In 1985 the Montana ANG won the Hughes Trophy. The 186th FIS was the last F-106 squadron to participate in a Red Flag exercise at Nellis AFB, Nevada, in 1986.

The squadron ended its F-106 era when its last two F-106Bs (57-2517 and 57-2530) left on 26 June 1987 for transfer to the 101st FIS.

The squadron patch with a bird firing two six-shooters was commonly known as 'Henry Hawk', although among some squadron members it was jokingly called 'Charlie Chicken'. Unfortunately that name Charlie Chicken is what made it onto the official 120th Air Wing's website under the HISTORY OF THE 120TH FIGHTER WING fact sheet.

Winner Hughes Achievement Trophy 1985