Can I pay a plane ticket with cash? And how?

You can buy your ticket with cash at a travel agent or airline ticket office at an airport. If you pay cash to a travel agent, be sure they issue your ticket and give you a receipt before you leave their office.

...and you do need a passport. If you're a Philippine citizen traveling on a Philippine passport you'll also need a visa issued by the US Embassy in the Philippines. It's probably best to get the visa first in case the US Embassy rejects your application. If you have a US passport, then just buy the ticket, you don't need a visa.

Um, if you can do it, you would have to either go to a travel agency or to the airport at the company's office. You'd need a passport (well, just the same stuff you used to come to philippines).

Go to the ticket counter. You can buy the ticket in advance that way also. Some airlines will let you reserve a ticket online as long as you pay for it within the next 24 hours.

Go online to find out which airlines have flights that you like, who has the best price, etc. Use the online service to check availability. I'm not sure the best online site to use from the Philippines. Try expedia.com or travelocity.com

Once you know which flight you want, go to that Airline's ticketing office and pay with cash. Bring your passport. Some airlines only have ticketing windows at airports, and some have separate offices.

The safest method would be to go to the airport, go to the "Ticketing" counter, not the check-in counter. It would be better if you checked for flight numbers and times on-line before going so that you know what to purchase. The ticket counter will be able to accept cash.

You will need your passport at the time you travel, and will need to display it when you check in for your flight.

You can go to the airport ticket counter or to a travel agent to book your flight and pay with cash (if you don't have credit card). You might need to bright your ID and passport in case they need to verify something. That's all.

You need your passport, yes. I am not sure how their payment system works in the phillipines. I can look it up for you and guide you through it if you want though.