Edit: The flights listed below are no longer available for those prices on those dates, but there are other dates available for a similar or lower price.
God Save the Points reported that British Airways and American Airlines have put premium economy tickets on sale between East Coast cities and Spain, Italy, and France. That caused me to play around with Google Flights (See: How to find great business class fares with Google Flights for tips), using the map feature to find other cheap pairs. I’ve found that Delta/Skyteam has also dropped fares on many routes to beat AA/BA in many markets — with round trip premium economy available as low as $601 round trip between New York and Zurich. Many other cities are also on sale. These are very good prices for premium economy fares — some of which could be upgraded to business class with miles / upgrade instruments based on availability.
Note that I found some of these did not have bookable links from Google Flights, yet I still found them through online travel agencies like Expedia, Priceline, and CheapOAir — so check one of those sites if you find dates and can’t book through a link at Google. These low prices can mostly be found for travel in April and May and then again beginning in September for fall travel — though as you’ll see below, some cities have good prices into early June. Examples to follow – click the city pairs or images to check for more dates / options:
Note that the Boston to Copenhagen itinerary is an example of one that did not show up as bookable via Google Flights:
Yet I had no trouble finding those same flights on the same dates via Expedia.com:
Some of these — like $601 round trip to Zurich in Premium Economy — are terrific fares for a seat with a little more space. Some fares are upgradeable with miles or upgrade instruments, but you’ll want to check with the loyalty program of the airline with whom you’re booking for rules and availability. While economy tickets to Europe often pop up in the $350-$500 round trip range, many will find it worth the small premium to have more space, potentially earn more miles, and maybe even use miles/points to upgrade. Remember that if you book through most online travel agencies, you should have 24 hours to cancel without penalty (but always check the terms).