Working at ONT, I see that a lot as well.
It is mostly the northerly arrivals that slam dunk in, since they have to cross the san bernardino mountains, which top off at 10,000 on that approach, then they dive in, and they cross PETIS at around 6,000 feet. This does not give them much room for error.
I have flown Over petis in a 152 inbound to ONT, and the glideslope intercepts at 4,000 so you have to lose altitude FAST in order to make it.
The C-5's you saw were there for a convention with Dubya himself. They brought in/out all his things.
When AF1 was within 10 miles of ONT, they shutdown the airport, and NOTHING on the AOA was allowed to move, not even the ops personnel.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.