A-4 and S-2 are already Supersonic due to being able to keep up with a F-15 Eagle but their are other feats that show this.
A-4 states that he and S-2 could fly to LA from Area 51 in 13 minutes which they would've have done it if the military didn't stop them with five F-15 jets. If we serch the distance from Area 51 to LA we get 260 miles and using a speed distance calulator we get 536.448 m/s which is Supersonic.
In another instance A-4 and S-2 travel from Anaheim to LA in a minute but are stopped by J-1 and A-5. If we use this site to see the distance from the Anaheim Convention Center to LA we get 41 Km and using a speed distance calulator we get 683.333 m/s which is Supersonic.
Bonus: J-1 and A-5 travel speed to stop A-4 and S-2. For this feat we'll assume that J-1 and A-5 were in Area 51 and intercepted A-4 and S-2 at Hacienda Hills which is 24 Km from the Anaheim Convention Center which is around a 35 second travel time. Using this, they would need to have traveled 255 Mi in less time so we'll say they traveled in 30 seconds which is 13679.4 m/s or High Hypersonic.