Below is a complete list for the locations of all minikits in Chapter 06: Avengers Assemble.
Part A MInikits
Minikit #01: You can spot this collectible at the top of the screen while flying the aircraft.
Minikit #02: After Loki flies off, search the top floor of Stark Tower for an electric panel that Thor can power up to make the minikit appear.
Part B MInikits
Minikit #03: Search the streets for three fire hydrants and destroy them.
Minikit #04: Look for a sports shop at the southwest corner of the area and have Captain America extinguish the flames in front of it. Create a red handle from the bricks that appear and have Hawkeye pull it to open the door.
Minikit #05: There is a police car in the area that you can fix using either Ultron or Tony Stark. Do so and drive the car toward the bus at the end of the road to get this minikit.
Minikit #06: Keep an eye out on the street for a blue car that you can destroy to find a vent underneath. Send Vision through here so you can get inside one of the shops to collect this minikit.
Minikit #07: This collectible is hidden in the van next to the Collector's location. Simply use Ultron's powers on the vehicle and destroy the box inside.
Part C MInikits
Minikit #08: After saving the final batch of civilians, there's a green car in the area that is blocking a vent under it. Blow this car up so Vision can access the vent then have a character that can dig locate a total of three digging spots. Finally, take someone who has telekinesis and set the statue pieces back onto the clock to claim this collectible.
Minikit #09: For this minikit, you need to use telekinesis to move or manipulate a total of three planters in the area.
Minikit #10: In the area with the Deflection Pad, you need to destroy all of the Chitauri ships using Iron Man's lasers.