Relying on seeing another aircraft in the air at night is pretty much a disaster waiting to happen. You don't see aircraft at night, you see lights. And they'

Relying on seeing another aircraft in the air at night is pretty much a disaster waiting to happen. You don't see aircraft at night, you see lights. And they're over a city--a gazillion lights. Thus all you really see are moving lights. But if two objects are on a steady collision path neither moves relative to the other. Thus both sets of pilots would simply have seen stationary lights, invisible against a sea of stationary lights.