Major airlines serving the Miami–Barcelona market or providing competitive one-stop options include American Airlines (partner codeshares), Iberia (via Madrid connections), Air Europa, Level (seasonal/low-cost long-haul), and other European carriers. American and Iberia offer strong transatlantic networks with premium cabin options; low-cost carriers like Level may provide lower fares for no-frills travelers. When comparing, consider fare classes, baggage allowances, layover airports, and total travel time. Use keywords like 'American Airlines Miami to Barcelona January', 'Iberia Madrid connect MIAA to BCN', and 'low-cost long-haul Level BCN' to find the best match.