Ok, can/could F-4 maintain a constant airspeed in the vertical?
An F-4 in a vertical climb was losing speed. An empty F-4E weighed 32,000 lbs. Fuel, crew, external tanks etc added weight. In theory, a completely stripped down F-4 could have a 1:1 thrust:weight ratio...moments before flaming out. Going up vertically with no fuel left would be bad.