1-He is exempted from fasting!

2-He should fast if it will be easy!

3-He can take his breakfast in his house before leaving!

4-If he fasts and the flight takes-off before sunset, his current weather overrule his country weather!

5-That is, he leaves by 6pm but while on flight his current weather says 10am, he observes the sunset of the current weather before he can break the fast!

7-Calculatively, 1hr is left for him to sunset in his country, the sunset of his current weather 8pm, then he would have:
1hr+10hrs =11hrs to break the fast! That means, he fasts for 24hrs!

8-If a flight has a stop-over and the sun sets in that country all fasting travellers must break their fast by that current weather!

9-If he observes the sun after taking off from the stopover, he should continue his eating and drinking!

10-If he begins his fast in the stopover then later while on the flight the sun sets, then he must break his fast !

11- Those who live in a country where there are Fajr and the Sunset must start the fasting from the True Fajr and break at the Sunset !

12- For 11, regardless of the hours in between like the Scandinavian countries with 23 hrs of fasting sometimes or 3 hrs of fasting !

13- Those who live in a country where the night or day covers 6 months or less or more, the time-range of the neighbouring countries should be employed !

14- A traveller in a country where the calculation of the fasting-days are not tallied with his own country, the current country's calculation must be followed !

15- He must complete the missed days after Ramadaan; e.g, A man of 28 days of fasting travels to a country of 29 days of fasting, if the moon is sighted, he must celebrate the 'eed with them and pay the missed days later !

16- If the moon is not sighted, he has to pay a day back as the month is 30 days !

References for the analyses above by the Scholars are:
**Q2:187
"...and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night), then complete your Saum (fast) till the nightfall"

**When is it lawful for someone fasting to break the fast?

Hadith no :1890

Narrated `Umar bin Al-Khattab:

Allah's Messenger said, "When night falls from this side and the day vanishes from this side and the sun sets, then the fasting person should break"

Bukhāry.

Also check:
Muslim no1842, Abu Dawud no 2005, An-Nusaa' no 864 and Musnad Ahmad no 320.