Flights to Europe have been dirt cheap this summer. A handful of airlines offering ridiculously low prices, keep driving the cost down. Primera Air, which recently expanded into the US, is one of those budget airlines, and it's offering $69 one-way flights to Paris and London in its "last-minute sale."
Many budget airlines offer low one-way prices and have slightly higher rates on the return journey. That's the case here. There are absolutely $69 one-way flights, but the return journey can be a good deal more expensive. However, if you have flexible timing for your trip, you can find return fares between $119 and $243, which still makes for a cheap round-trip flight between the US and Europe.
With fares this appealing, the deals aren't going to last long. The prices are current at the time of publication, but you should expect the selection to thin out quickly. That means the cheapest tickets are going to disappear in a hurry. You'll find $69 one-way flights from New York to Paris, Boston to Paris, and Boston to London. It looks like that price is already gone for the New York to London treks. Though, you can still find $109 flights from New York to London, and $149 flights from Washinton DC to London.