As usual, Joe is most helpful.

 The source of the curfew is different at Pearson – there is no tripartite agreement, or anything similar, that sets very strict limits on what can be done.

 Here’s the precise wording:

 "The Lessee acknowledges and agrees that all flights into and out of the Toronto City Centre Airport shall operate between the hours of 6:45 a.m. and 11 :00 p.m., with the exception of medical evacuations and other emergency uses."

 The reason this was negotiated was to protect the surrounding neighbourhoods from noise during curfew hours. Allowing aircraft to taxi about, and line up for takeoff within curfew hours counters that purpose.

 In my view, the curfew wording would be interpreted by a judge to reflect its intended purpose – to prohibit all ground operations save emergencies, during curfew hours.

 Brian Iler