Judah writes:

If 160 people want to go from JFK to ORD on a Thursday morning at 8am, they
will fill a 737, but they will consume less than 1/3 of the seats on a 747.

If 1000 people want to go from JFK to ORD on Thursday, they'll fill two 747s
or ten 737s. The main difference is in how much fuel is wasted and how great
an impact on the environment is created.