Thopter Squadron has at least two +1/+1 counters on it.
({1} magic symbol) available.
Steps
Activate Thopter Squadron's first ability by paying ({1} magic symbol) and removing a +1/+1 counter from it, creating a 1/1 Thopter artifact creature token and a 1/1 Squirrel creature token.
Activate Ashnod's Altar by sacrificing the Squirrel, adding ({C} magic symbol) ({C} magic symbol) .
Activate Thopter Squadron's second ability by paying ({1} magic symbol) and sacrificing the Thopter, putting a +1/+1 counter on it.