3 hours by plane also includes 2 hours traveling to and from the airport, an hour of security queueing, and another hour of navigating the airport, boarding, and picking up your luggage. All those extra stressful hours are not available for working. Now you've spent the better part of a day traveling, just how much are you going to get done "the rest of the day"?
Get TSA Precheck, carry your luggage on (easy for work trips IME), learn the typical transit time and latencies for security. I can leave my house at 4:30-4:45 for a 6 AM flight (boarding closes at 5:45), reliably make it, have breakfast on the flight, and walk off the plane directly to ground transport and be in fine shape to work a full day somewhere.
You can add hours of buffer time if you want (if you're flying to do an organ transplant, maybe that's a good idea); most people can take a 0.5% chance of missing their flight. (I've literally never missed one, though I've been a few minutes away from doing so a couple times, usually because of my own error, once because of unexpectedly long security lines, even for TSA Pre.)
