If helpful did a quick scan at the 17 airlines in scope and if you would book directly through their website, if you are able to add the Eurobonus frequent flyer number from the get go. See the results below.

# Airline | Can Add EuroBonus Nr. | Date Checked
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1 Aerolineas Argentinas | Nope | 2024-10-16
2 Aeromexico | Nope | 2024-10-16
3 Air Europa | Yes | 2024-10-16
4 Air France | Yes | 2024-10-16
5 China Airlines | Yes | 2024-10-16
6 China Eastern | Nope | 2024-10-16
7 Delta Air Lines | Yes | 2024-10-16
8 Garuda Indonesia | Nope | 2024-10-16
9 Kenya Airways | Yes | 2024-10-16
10 KLM | Yes | 2024-10-16
11 Korean Air | Yes | 2024-10-16
12 SAS | Yes | 2024-10-16
13 Saudia | Yes | 2024-10-16
14 TAROM | Yes | 2024-10-16
15 Vietnam Airlines | Nope | 2024-10-16
16 Virgin Atlantic | Yes | 2024-10-16
17 Xiamen Air | Nope | 2024-10-16