When should those living in tall buildings break their fast?

Firstly: 

Islam has given a very clear sign for the end of the fast, which is the
setting of the sun beyond the horizon. Once the sun has set, it is
permissible for the fasting person to break his fast, because Allah, may He
be exalted, says (interpretation of the meaning): “then
complete your Saum (fast) till the nightfall”
[al-Baqarah 2:187]. 

The night begins when the sun sets, as has been explained in the answer to
question no. 110407. The Prophet (blessings and peace of Allah be upon him)
said: “When the night comes
from here (meaning from the east) and the day departs from here (meaning
from the west), and the sun sets, then it is time for the fasting person to
break his fast.”

Narrated by al-Bukhaari (1954) and Muslim (1100) 

An-Nawawi said: The fast ends and is completed with the setting of the sun,
according to the consensus of the Muslims.

End quote from Majmoo‘ Sharh al-Muhadhdhab (6/304) 

What is meant by sunset is when the entire disc of the sun disappears below
the horizon. There is no significance attached to the redness that remains
on the horizon. When the entire disc has disappeared, it becomes permissible
to break the fast. 

Al-Haafiz Ibn Rajab (may Allah have mercy on him) said:

This hadith indicates that that the mere disappearance of the disc ushers in
the time for Maghrib prayer, and the time for the fasting person to end his
fast. This is the matter of consensus among the scholars, as was reported by
Ibn al-Mundhir and others. 

Our companions, and the Shaafa‘is and others, said: There  is no
significance attached to the deep redness that remains in the sky after the
disc of the sun has set and disappeared from view.

End quote from Fath al-Baari (4/352) 

Shaykh al-Islam Ibn Taymiyah said:

Once the disc of the sun has set, at that point the fasting person breaks
his fast, as the time during which it has been prohibited to eat and drink
has now ended. The deep redness that remains on the horizon does not have
any impact on any of the rulings.

End quote from Sharh ‘Umdat al-Fiqh (p. 169) 

Secondly: it is well-known that the setting of the sun varies from one place
to another, and from one city to another. Likewise, it may vary in a single
location depending on whether one is in a low or high place.

As
Islamic teaching has connected the time of breaking the fast to the
disappearance of the disc of the sun, each person has his own ruling,
according to the place where he is at the moment of sunset. So he should not
break his fast until the sun has set relative to the place in which he is,
whether it has set in another place or not. So a person who lives in a high
tower should not break his fast, even if the sun has set for those who are
at ground level, until it disappears from the horizon as he sees it. 

Fakhr ad-Deen ar-Raazi said: It was narrated that Abu Moosa ad-Dareer al-Faqeeh,
the author of al-Mukhtasar, came to Alexandria and was asked about
one who climbs up the minaret of Alexandria and sees the sun a long time
after it has set for the people in the city; is it permissible for him to
break his fast? 

He
said: No, but it is permissible for the people in the city, because each of
them is required to follow the teachings in relation to his own situation. 

End quote from Tabyeen al-Haqaa’iq (1/321) 

Ibn ‘Aabideen said: It says in al-Fayd: One who is in a high place,
such as the minaret of Alexandria, should not break his fast so long as the
sun has not yet set from where he is looking, but the people of the city may
break the fast if the sun has set before that from where they are. The same
applies with regard to dawn in the case of Fajr prayer and sahoor.

End quote from Haashiyat Ibn ‘Aabideen (2/420) 

Muhammad Anwar Shah al-Kashmiri said: In the books of fiqh it is reported
that there were two men, one of whom was at the top of a minaret and could
see the sun, and the other was at ground level and the sun had set from
where he was looking. It is valid for the latter to break the fast, but not
the former.

End quote from Fayd al-Qadeer (3/355) 

In
Fataawa al-Lajnah ad-Daa’imah (10/297) it says:

Each fasting person is subject to the ruling on the place in which he is,
whether he is at ground level or in an airplane in the sky. End quote. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:

People who are on mountain tops or in valleys or in high buildings, each of
them has his own ruling. The one for whom the sun has set is permitted to
break the fast, but the one for whom it has not set is not permitted to do
so.

End quote from ash-Sharh al-Mumti‘ (6/398) 

And he said:

If
the mu’adhdhin gives the call to prayer but you are in a high place and can
still see the sun, then you should not break the fast.

End quote from al-Liqa’ ash-Shahri (41/22) 

The same applies for passengers on board a plane: they should not break the
fast until the sun has set from where they are looking. 

The scholars of the Standing Committee said:

If
a fasting person is on board a plane and he can see from his watch or cell
phone that a nearby country has now broken the fast, but he can see the sun
because of the altitude of the plane, then he does not have the right to
break his fast, because Allah, may He be exalted, says (interpretation of
the meaning): “then
complete your Saum (fast) till the nightfall”
[al-Baqarah 2:187]. And
this has not been fulfilled in his case, so long as he can still see the
sun. 

End quote from Fataawa al-Lajnah ad-Daa’imah (10/137) 

Shaykh Ibn ‘Uthaymeen was asked: In the month of Ramadan, we may be on a
journey and we fast during the journey, then night comes when we are still
in the air. Should we break the fast when we see the disc of the sun
disappear from in front of us, or should we break the fast according to the
timetable of the people of the city over which we are flying? 

He
replied: Break the fast when you see that the sun has set, because the
Prophet (blessings and peace of Allah be upon him) said: “When the night
comes from here and the sun sets, then it is time for the fasting person to
break his fast.” 

End quote from Majmoo‘ Fataawa wa Rasaa’il al-‘Uthaymeen (15/437) 

Please see also the answer to question no. 106475

To
sum up: 

Those who live in high buildings should pay attention to the differences in
time between sunset at ground level and in the place where they are. 

The Department of Issuing Fatwas and Islamic Affairs in Dubai has explained
that the residents of Burj Khalifa, which is 160 storeys high, are required
to delay breaking the fast in the month of Ramadan, and those residents who
live on floors 80 to 150 are required to break the fast two minutes after
the time of the adhaan for Maghrib prayer. 

For those residents who live on floor 150 and above, the time for the adhaan
of Maghrib and ‘Isha’ prayers is three minutes later. 

For those residents who live on floors lower than the eightieth floor, they
may break their fast according to the time of the adhaan for Maghrib in the
mosques. 

Please see the following link: 

http://www.emaratalyoum.com/local-section/other/2011-08-06-1.414355

or 

http://www.aleqt.com/2011/08/06/article_566738.html

And Allah knows best.