Please choose the correct ending to complete the given sentence: Travel: [header] How to travel the world on $50 a day [title] Research what airline has the most flights out of your home airport. [step] Also, choose a major airline, like delta or united, that partners with international airlines to go all over the world. If you need to go to a hub to get flights, survey the cheapest connecting flights.

Ending1: [title] Choose a small airport on the basis of availability. [step] Instead of booking flights with thousands of carriers, you might want to connect your e-ticket to delta or united. Ending2: Start booking autofares to and from home as early as possible. [title] Find a city close to your home, or that has no airport. Ending3: [title] Sign up for a mileage credit card with this airline. [step] Ensure your credit is good and that you can handle a revolving credit account. Ending4: [title] Use smartphone apps to keep track of how many tickets you earn in one day. [step] Always remember to study websites like airfare.

Answer format: ending1/ending2/ending3/ending4