Empire of the Sky DLC
Squirrel #24: Stratosphere
Start at this checkpoint with the green laser beams, after which you get launched out into space.
Bailout off the ramp on the opposite side, to fling yourself upwards.
Float up then push left to land on top of the large rock hovering above you with a fancy squirrel pad on top.
Squirrel #25: Winter Getaway
On the other side of the initial pool, start on this ramp outside the building.
Bailout off the ramp above then push up to fly onto the roof of the building behind you, aiming for the opening on the right.
Fall into the opening and a squirrel will appear.
Squirrel #26: The Substratum
Stop on the A9 platform, then roll backwards to drop off.
Land on the ramp below and ride into the doorway covered with laser beams.
This will transport you to a moonbase where the last squirrel appears.