with cte as
(select id_vzlet, id_posadka, 1 as [level], cast('-'+id_vzlet+'-'+id_posadka+'-' as varchar(max)) as path
from marshrut

union all

select cte.id_vzlet, m.id_posadka, cte.[level]+1, cte.path+cast(m.id_posadka+'-' as varchar(max))
from marshrut m inner join cte
  on cte.id_posadka = m.id_vzlet
where cte.path not like cast('%-'+m.id_posadka+'-%' as varchar(max)))

select * from cte
order by [level], id_vzlet