I am flying from the USA to Switzerland with a one way ticket. I will also be flying from Switzerland to Spain and be traveling around in Europe but I do not have a return ticket because I am not sure from which country I will be departing from. Would this be an issue for the airlines?
I am flying through American Airlines and Iberia.
When entering the Schengen area as a non-EEA citizen, you do not need proof of onward travel, but proof of "means of subsistence ... for the return to your country of origin or transit to a third country into which you are certain to be admitted" (Schengen Borders Code, Article 5). An onward or return ticket would of course also fulfill this requirement, but money to buy a ticket after entering the Schengen area is also enough.
As others have suggested, it may however be a good idea to check with the airline if they have additional requirements.
Arriving in a country for a "visit" without a return (or ongoing) ticket usually raises the suspicion of the immigration officers. They may think that you are not actually intending to leave. The airlines are responsible for your return transport if you are refused entry into a country, so the airline has interest in avoiding you getting refused entry at the destination. Therefore, the airline might require that you have a return or ongoing ticket before boarding your flight.
At this point you should call your airline and confirm that your eligibility to board the plane. If they require that you purchase another ticket, you can buy a fully-refundable future ticket and then refund it later (after your flight). I've had to do this once before and if you have sufficient room on a credit card, it's not a big deal.
The airlines will not care. The officials in the country of arrival, however, may.
I have done this twice going to Europe. When you enter, the officials want to know how long you will be "in [their country]". Answer truthfully, which in your case must be a few weeks or so.
The only time I had trouble was when, cycling to Canada, I said "I don't know how long I'll be here." Obviously a poor answer.
