Does anyone know if Pacific Southwest Airlines (PSA) ever flew certain routes under VFR?
I've read this question and I understand that Part 121 does allow for VFR flight, but my question is specific to PSA. I've heard they routinely flew low altitude VFR flights on shorter routes throughout California.
I was a controller at L.A. Center around that time, and it was extremely common for airlines on the short-haul routes to go VFR-on-top, which is VFR but on an IFR flight plan. There would have been a lot of downsides to flying VFR but every advantage to them to fly VFR on top: with on-top they didn't need clearance into class B (back then the TCA) or get refused or delayed because the controller was "too busy"; didn't have to fly airport patterns (basically guaranteed a straight-in since they would be on an instrument approach); and for flying into the metered airports like LAX or SFO they would have a guaranteed slot, unlike trying to call up as a VFR where they would go to the back of the line and might have to hold for an hour. Plus of course on-top has the benefits of not needing IFR separation, so ATC would almost always give them a direct routing and they could climb all the way up to 16500/17500 instead of being step-climbed under everyone else and capped at maybe 10,000.
So while I don't remember specific routine flights from 25+ years ago, I do remember working a LOT of airlines flying VFR on top on the short routes like LAX to Bakersfield, Burbank to Fresno, etc.
Well, there is nothing to indicate in 14 CFR 121 or 135 that an aircraft cannot operate under VFR for a revenue flight.
For very short hops at low altitudes in good weather, a VFR flight can make a lot of sense since it is simpler to conduct, adds less congestion to ATC and may allow the flight to reach its destination more quickly.
For most revenue flights for regional, transcontinental or intercontinental destinations, an IFR flight is preferred, or even mandatory, due to uniformity in ATC routing, operations at high altitudes - Class A or equivalent airspace - and greater operational flexibility in marginal weather.
It's important to understand the difference between visual procedures, visual flight rules, and visual meterological conditions.
Airliners always operate under instrument rules because it guarantees them ATC services, and because it's a requirement for proceeding into instrument meterological conditions (IMC). Also, higher airliner flight level altitudes are reserved for planes on instrument flight plans.
In instrument meterological conditions, only instrument procedures are used. But in visual meterological conditions (VMC), airplanes operating under instrument flight rules (i.e., those following instrument flight plans) are often required to perform visual procedures like flying visual approaches, or maintaining visual separation from other airplanes.
