This is a fantastic deal, and will not last long. Already there are limited flights/dates available. I recommend searching for flights via Google Flights, since you can get a two month calendar view of the days with the cheapest flights.

The cheapest fares I saw from PHL to LAX was $150, but other inexpensive fares are available, some under $200. If you want to go to San Francisco, the cheapest flights are pricing out at $206 round trip. Limited cheap fares are also available to San Diego. You may be able to also find good deals on flights out of NYC to the West Coast. Play around with Google Flights to find something that works for you!

To get the fare, you will have to book through Orbitz after clicking through Google Flights (you can not go direct to Orbitz and get the fares from what I have seen). These economy flights are all on American Airlines and most have a connection through Chicago or Denver.

Here are some example searches:

Philadelphia to San Francisco for only $206 r/t in March!

Philadelphia to LAX for only $150 r/t in Feb and March

Philadelphia to LAX for only $150 r/t in May ($197 in April)

Want an even better deal?

You could actually get these flights for free! If you have a card like the Citi Prestige Credit Card since it offers an annual $250 credit towards airline purchases. Although the card has a $450 annual fee, the $250 credit offsets the majority of this, and the lounge access and other benefits often make up for the rest of the fee depending on your travel habits.

Let me know if you have any luck booking these flights!