I have a trip booked to Osaka Japan from Boston with United. I'm planning on getting a new credit card for the trip since it will be about 3 weeks and will be spending plenty to hit the sign up bonus. Should I get a united mileage card and build more miles/points with united? Can I combine my frequent flyer miles from united with my points from the card? Or should I start building points with another airline like American Airlines which look like they might become my go to airline later on. thanks, happy travels!