This is used by United Airlines for trip updates (e.g. delayed flights) and trip reminders (e.g. flight boards in 3 hours).  In one's online web "profile" at united.com, it is trivially easy to configure it not to call during specified hours (e.g. when one is sleeping).  This is NOT a spam, advertising, or other solicitation telephone call.

Legitimate call from United Airlines inviting me to check in for my flight tomorrow

Calls & hangs up with no message [I don't pick up calls from spammers!]
This is not a legitimate call if they are telling others they are from Continental Airlines - I am not now nor ever  flying with Continental!
Re-verified my phone was on Do Not Call list so I can't register a complaint.
I hate spammers!

Received a bogus voicemail from this number this morning saying that I could check in early for my upcoming flight from SF (which would actually be my departure city) scheduled on Oct 29th. I panicked, thinking it was real, so I checked the confirmation code they left in the voicemail and it was definitely fake. WTF?

Sounds to me like your phone number is on some regular traveller's profile, and every time they book a flight you start getting calls, have you tried calling the airline?

They must have called a wrong number--no one left a message, but I am not flying on Continental and have not used that airline for about 20 years.

A flight reminder from United Airlines.

United Airlines Confirmation clall

I just got an automated call from this number.  It said the call was from United Airlines and it was a reminder that I could check in early for a flight tomorrow.  Except I'm not on that flight and don't live in the departure city.  But a family member IS on that flight and she listed me has an emergency contact.  The flight was booked through Travelocity so I know if they screwed up contact information or if UAL did.

I'm not Mary and I haven't booked a flight - what about the poor woman who DID???   This airline has called before ( I'm not Marty either!) - Whats wrong with them???Don't they know ANYBODYS number?

I repeatedly get call from this number.  I know its an airline, but I have not booked a flight in years.  I have no idea how they have my number.  Its calls multiple times a day....thern stops for a couple weeks, then starts back again.

robo-call, no one there when I answered.

Yeah, United for me.  I have a flight tomorrow, in about 22 hours.  It wanted me to check-in over the phone, but I hung up.  I'll do it on the web.

Now that United Airlines and Continental Airlines have merged, this is the United Airlines phone check-in service. I got a call from this number about twenty hours before my United Airlines flight.

I've also received an erroneous automated call (today, April 23rd) from this number which included the flight confirmation code.  As per @plants above, yes, that is very insecure, especially if the code can be used to cancel or change the flight, change the passenger, or send a refund to some arbitrary address.  They should use encrypted email or something similar, presuming it truly is UA.

Now its United calling...left 2 messages to confirm flights,one from san diego,the other from chicago...left the confirmation codes in the VM also...thats real secure!  seeing as I never booked a flight in over a year...hope the actual person realizes there's still honest people out there...

Got a call from United about an upcoming trip.  Never had them call me before, but now that Continental and United have merged, I guess this will happen more often.  I just wish legit companies would put their name in the Caller ID and not just leave it as Toll Free.  Still annoying.

Got two calls today from this number on a phone number I rarely use. I do not fly continential airlines so this is troublesome.

Called 730am on a Sunday. Never flown or will fly continental.

Got a call at 2am. Woke me up. Said it was continental, but we have no one flying continental right now. Caller id said milwaukee county....not happy at all, they need to fix this!

I receive a voice mail from this number. It said it`s from Continental but the strange thing is I didn`t book a flight from this airline. It`s weird

this call woke me up at 1:30am. i have no flights with continental tomorrow or ever in the future (or ever in past since i've been at this number).  i called anyway to verify since a couple kids are out for the night.  continental airlines has no idea why my phone number is in their computer.  they left a voice mail on my answering machine (cannot understand it... a recording).

I am flying Continental tomorrow and they called me exactly 24hrs before my flight to let me know I could check in online from this number.  I did check in online this morning at around 8:30am....just got another call with no message from the same number at 4 something pm.  Dont know why they would have called again but still nice that they remind you.

This is a number for Continental Airlines.  I think it's the automated trip alert number.

I received 2 phone calls from that phone number since yesterday. Don't know, who they are, why they are calling. If they keep calling I will report them to the do-not-call list.

Continental Airlines - they confirm your flight information and leave you the confirmation number, so you can check in online.

Yes, it's Continental.  Their system called me once and hung up (or just didn't leave a message).  One hour later came their call reminding me that I could check in on-line.

It's Continental Airlines - flight reminder service

Right, Continental  Airlines automated call to confirm flight details.

Got my call at 12:05 AM, woke me up too.  Our flights do not leave until late MAY.  I am calling and complaining at the highest level as this also involves 8 calls to Continental/UnitedI have made because of screwed up reservations for that trip.