Hello - my ultimate goal is to get to Salamanca, Spain and I have found 2 tickets that will get me there the cheapest from Austin. 1 flies into Dublin airport on Aer Lingus at 4:55 am and I found a Ryan air ticket that departs at 6:25 am from the Dublin airport to Madrid (pease note these would be booked separately). Once we get to the airport we will be taking the Avanza bus to Salamanca. The other option is to fly into Frankfurt and land at 3:05 pm on Condor and take a Ryan air flight at 4:40 pm to Madrid. Both layovers are around 90 minutes. I’ve done some research and realized that both will require changing terminals and I am still unclear on whether we will have to go through customs/passport control. Are either doable? My next best option is $500 more so please keep that in mind. We will each have a carry on bag.

Consider risks vs benefits. Benefits: $500. Risks: If anything slows you up connecting to the next flight, you lose the second flight and its return flight and must buy a pricey walk up ticket to your destination on a later flight, if available, perhaps requiring an overnight in transit. Because your tickets are not connected, getting to the second flight before the gate closes is at risk of weather delays, long lines, slow connection between terminals, etc. Also, the second flight is not required to honor the baggage limits (checked if you are foolish enough to think that you can collect and recheck a bag for the second flight, or size/weight of carry on) of the first flight, leading to overweight charges. These risks occur on both the going and the return flight itineraries.

Not recommended.

The problem is both options have unprotected flights. Very risky. RyanAir has a firm policy that boarding closes 20 minutes prior to departure time. You can have your boarding pass in hand, have carry ons only and get to the gate 18 mins early and you are SOL. From RyanAir's website: >>We can’t delay other passengers who arrived at the boarding gate on time, so passengers arriving late at the boarding gate will not be accepted for travel.<<. . .

And in that case, they have no responsibility to get you to your destination . . . Do you feel lucky?

we were posting at the same time . . . in other words - don't do it . . .

I have had 90-minute layovers in Frankfurt but all on one ticket. Check Iberia over Ryan air. I bought last minute tickets on them in October and not a bad price. They didn't blink an eye at my 20 inch carry on and big purse where Ryan air would.

Assuming you're a non EU citizen no chance.

You'll need to exit the secure area. Find the Ryanair help desk. Get your ID checked. Your boarding pass stamped. THEN clear security. Find your gate. It's been mentioned but boarding closes before departure. Those planes will have pulled away from the terminal at departure time.

Iberia has been mentioned. On those short hops expect an Iberia ticket to mean a Vueling operated flight. No point paying Iberia prices to sit on a Vueling flight.

Can't you fly to one of the Norwegian cities (NYC for example) and then fly to Barcelona with them.

I would never plan such a short connection on a flight that wasn't protected. Even if it weren't for all the factors mentioned above, suppose your first flight arrives late? To see what it might cost you, check out the price of a last-minute ticket (for today) on the Ryanair flight you're planning to take. If it's an amount you can tolerate, go ahead and take the risk. But there's no guarantee the cost won't be even higher.

The idea of flying to New York and getting a Norwegian Air flight is good advice. They have excellent planes; my daughter used them for her most recent round trip to Italy, and we're going to use them for our next round trip to the US. Just remember, everything costs extra on their flights. Also, I don't think they have any code shares, so this will also be an unprotected transfer. If you search for a ticket on www.skyscanner.net they will find you unprotected connections that are insured. They all have very long connection times, though. On the way over, my daughter's first flight arrived in New York eight hours before her departure for Rome. On her way back, her connection involved an overnight at Newark.

I had a short hop from Stuttgart to Madrid and had Iberia. Just saying because of the baggage carry on. How is vueling with bag charges?

Depends on the class of ticket you book. It's all on the website