On all flights which provision North American meal standards (including Mexico and the Carribean), all bread is heated in oven proof packaging. There is a breakfast standard (sweet and savoury) and a lunch/dinner standard (savoury - two types).

On International flights departing YYZ/YUL & presumably now YVR as well, bread is freshly baked and delivered to the flight kitchens. It is french style bread (baguettes & multi grain crusty rolls), and the supplier specifications advise that the bread NOT be heated -- believe it's Ace Bakery or similar. Heating a baguette after they've been baked cause them to turn rock hard. For years the catering specifications out of CDG & FRA have also stated that the breads not be heated to maintain it's crusty consistency.

Sounds quirky, but there is a method to the madness. In a french restaurant, how often are heated baguettes served??