Boissy-l'Aillerie is a commune in the Val-d'Oise department in Île-de-France in northern France.

Pontoise – Cormeilles Aerodrome is located in the commune.

At one time Aigle Azur's head office was on the grounds of the airport.

The average annual rainfall is 635.8 mm (25.03 in) with December as the wettest month.

The temperatures are highest on average in July, at around 18.9 °C (66.0 °F), and lowest in January, at around 4.3 °C (39.7 °F).