Customer service. I typically do not fly United and if this is indicative of their customer service, will not in the future. After purchasing my ticket I needed to add my KTN number and spent 25 minutes on hold, NEVER receiving response. Not having the luxury of waiting longer, I called again with a required 20 minute wait! I had to hang up before they answered. (With Delta someone pleasant and efficient always answers within 10 minutes.) United is unprofessional and inconsiderate to clients in this regard. It's easy to make a sale and take money but the measure of a good company is considerate customer service and respect of the client's time. 20 to 30 minute waits are disrespectful indifference! This is the last time I'll fly United.