With flight delays prevalent, many travelers are opting for seven-hour drives.
I've drawn a 6-hour travel circle around the office. Anything inside the circle is "drive" and anything outside is "fly." The reason is simple: Even a "short" 2-hour flight (like to DFW) will take 6 hours when you count drive time to the airport, getting through security, etc. Also, any flight before 9:00AM incurs an extra day of per-diem for an overnight at the airport. (Gone are the days of getting up at 0-dark-30 for a 6AM flight!)
The corporate mileage rate has also increased dramatically to account for $5.00+/gallon gas.