I received an email from our travel agency that my flight was flagged for back to back reservations and that my flights may automatically cancel.

I had a round trip ticket from EVV-VIE from Sept.- Feb., and while in VIE, I have reserved an additional round trip flight from VIE-EVV from Dec.- Jan.

Is there any issue with these reservations?

No this looks fine. Back to back ticketing is usually used to get around minimum stay requirements.

Depends on why you're doing it. If, for instance the Sept-Feb fare requires a 6 month stay (I'm sure it doesn't, just giving an example) then you would be violating the rules. A fare for a stay of 3 months might be more.

A computer flagged you. What you have to show is that your two tickets are not lower priced than EVV/VIE R/T Sept.-Dec. and EVV/VIE R/T Jan.-Feb. And specifically not lower priced because you're violating fare rules to do it.

You went through a travel agency. Make them deal with it for you.

Welcome to FlyerTalk !

Without specific information such as the air carrier(s) between EVV and VIE, the fare buckets and fare rules, it is hard to provide solid information.

But, as a general matter, most carriers prohibit ticketing which has the effect of evading fare rules including advance purchase, location of purchase, minimum stay and the like. Why you are doing this is unimportant. All the carrier(s) care about is that your booking pattern violates the COC (contract) to which you agreed.

Your TA ought to have caught this as it is what it is paid to do. And, it is entirely correct that the carrier(s) may well cancel all tickets and also take action against your FF account(s). Alternatively, the carrier(s) may also debit the TA for the cost of tickets which do comply. But, that is not your problem.

Why not come back with sufficient information and you can get some specific assistance.

I knew nothing about back to back ticketing prior to this...I simply had to do a 6 month assignment for work in VIE so booked flight for the 6 months, and have now decided to go home for Christmas holidays..unfortunately when I contacted the travel agency regarding this they said everything would have to be re-booked and wanted to charge me an additional $1400.

Is it an actual possibility that Delta will automatically cancel my flight because of this?

You could always use a different airline for one of the trips.

The flights are through Delta/KLM, but the fare class I am not sure. I made the reservations through the TA's online website, in which case they are claiming that is why they did not catch it and are wanting to charge for rebooking/fare increase/etc....should I contact Delta directly to see if they will be cancelling my flights?

Others may have a better idea whether this is coming from DL through the TA, or just from the TA...but I would call them back, see if you can speak to a supervisor or someone above the front line agent you've probably already talked to - and specifically walk them through what Tchiowa describes (which is something I think a good TA would have done on their own as part of looking into this)

It might be simpler to tell the TA that you no longer want to return over Christmas, and simply then book the return on a different airline through another source.

The one time I did it, where I probably did breach the Saturday night stay rule, I booked the main round trip on UA as a revenue ticket, and the nested trip on AC using UA miles.

1. Do not call DL. No front-line person there has the authority to tell you what DL will or won't do. And, they have no authority to change a TA-issued ticket anyway. You can only make things worse, not better.

2. Call the TA and have the TA explain exactly what it is about the proposed ticket which causes a violation of the fare rules. Given the timing here, I suspect that it has something to do with minimum stay at VIE.

3. Presuming that you cannot budge things, book your holiday ticket on other carriers. And, book directly online and do not involve the TA at all.

^^