In 1878, Patrick Alexander, doubtless encouraged by his father, built an elastic driven model aeroplane of the Penaud type. In the late summer of that year, Patrick was taken by his father to see the Paris Exhibition. One attraction was irresistible: the enormous hydrogen balloon of Henri Giffard, which was capable of taking 52 passengers at a time on a tethered ascent to . The experience left a deep impression on Alexander, then 11 years old.