Tap Air Portugal has round-trip flights from Chicago (ORD) to Lisbon or Porto (LIS, OPO) for $499-$500. Lisbon flights January, February, and May. Porto flights January to March. 7-day minimum stay required.
Some small OTAs on Skyscanner and Kayak have this for as low as $482; which is cheaper than the airline. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.
Lisbon flights are NONSTOP. Porto flights have a connection in Lisbon.
Carry on bag with a maximum weight of 17.6 lbs is allowed for free on TAP. You can avoid seat selection fees by accepting the randomly assigned seat at the gate. Upgrading to a higher fare class that includes a carry-on bag for $65 may be cheaper than booking the “Discount” fare with the added $95 carry-on bag fee.
Flights on TAP allow for a free stopover (up to 5-days) in their hub city. This will be useful if you want to spend time exploring Porto or Lisbon before heading to your final destination. Link: More details on the TAP stopover program.
Click for more details and booking links Cheap Flights: Chicago to Lisbon or Porto $482-$500 r/t [Jan, Feb, May / Jan-Mar] – Tap Air Portugal