These are the fares avalible for your dates
Code:
TA14NW US One-Way 179.00 (USD)
TA7N2W US One-Way 183.00 (USD)
SIA14NI US One-Way 199.00 (USD)
SA7N1W US One-Way 213.00 (USD)
LA7N1W US One-Way 243.00 (USD)
WA7N1W US One-Way 303.00 (USD)
VA0R1W US One-Way 332.00 (USD)
NA0N1W US One-Way 432.00 (USD)
AA7UPN US One-Way 674.00 (USD)
M6 US One-Way 704.00 (USD)
AA0UPN US One-Way 764.00 (USD)
B6DM US One-Way 917.00 (USD)
Y6 US One-Way 1014.00 (USD)
YUP6 US One-Way 1224.00 (USD)
F6 US One-Way 1474.00 (USD)
Y US One-Way 1629.00 (USD)
F US One-Way 2511.00 (USD)
And here is the Availability for the flight you want.
Code:
US 1423
05/03/07 06:05 PM PHL
05/03/07 09:14 PM LAX
321
F9 A6 P6 Y9 B9 M9 H9 Q9 N9 V9 W9 L9 S9 T9 G9 K9 U1 E1 R1
So basically im not seeing either fare you posted as being valid.