Should I take a bus instead of flying?

Only if you have an extra 22 hours and a very high tolerance for winding mountain roads. Flying is the standard choice for most travelers; the bus is only recommended if you are trying to acclimatize slowly by stopping in intermediate cities like Arequipa or Puno.

Does my airline need to be different from my international carrier?

No, but if you booked an international flight on LATAM, keep your Cusco flight on the same booking reference. It simplifies baggage handling and priority rebooking.

Booking flights from Lima to Cusco for optimal altitude adjustment

Book a morning flight between 7:00 AM and 9:00 AM to allow your body to adjust to the 11,152-foot elevation throughout the day. Avoid flying in the late afternoon, as peak altitude fatigue often hits just as you are trying to navigate evening logistics in a new, high-altitude city.

Select the right airline. Stick to LATAM, Sky, or JetSmart. LATAM has the highest frequency and is the most reliable for rebooking if weather causes the common afternoon ground delays in Cusco.
Prioritize morning slots. Cusco weather is most stable in the morning. Afternoon flights are frequently delayed or canceled due to high winds and cloud cover over the Andes. Aim for a flight departing Lima by 8:30 AM.
Book a 'Flex' fare. Even if you are on a budget, pay the extra $20-$30 for a flexible ticket. Mountain weather is unpredictable; you want the ability to shift your flight to the next morning without paying a 100% fare difference if your original flight is grounded.
Select a window seat on the left. When flying from Lima (coast) to Cusco (mountains), the left side of the plane (seats A/B) offers the best views of the snow-capped Andes peaks during the final 20 minutes of the flight.

Should I take a bus instead of flying?: Only if you have an extra 22 hours and a very high tolerance for winding mountain roads. Flying is the standard choice for most travelers; the bus is only recommended if you are trying to acclimatize slowly by stopping in intermediate cities like Arequipa or Puno.
Does my airline need to be different from my international carrier?: No, but if you booked an international flight on LATAM, keep your Cusco flight on the same booking reference. It simplifies baggage handling and priority rebooking.