From the official site:
Manchester United v Maccabi Haifa Wednesday 18 September, KO 7.45PM and Manchester Untied v Olympiakos Piraeus FC Tuesday 1 October, KO 7.45PM
SALES TO SEASON/LMTB HOLDERS:
Sales will commence to Season/LMTB Holders who can purchase their own seats at the times stated below on production of voucher 22 (Maccabi Haifa) and 23 (Olympiakos) (duly completed) and their membership card. Alternatively ST/LMTB Holders unable to make a personal application can purchase their own seat by telephoning the MUFC Ticket Line on 0870 442 199 at the same times giving details of their customer number and credit card (please note an administration fee of 3% per transaction is charged) or by making an immediate postal enclosing letter of application, relevant voucher (duly completed), first class sae and open cheque (made payable to MUFC)
Sunday 1 September 9am until 1pm
Monday 2 September 9am until 5pm
Tuesday 3 September 9am until 5pm
Wednesday 4 September 9am until 5pm
ALL SEASON/LMTB HOLDERS WHO HAVE REGISTERED FOR THE AUTOMATIC CUP SCHEME SHOULD NOTE THAT TICKETS WILL BE PROCESSED DURING THE FIRST WEEK OF SALES.
Block 226 / rows 31–34 / seats 86–99 have been reserved for press overflow facilities and Season Ticket Holders in this area are requested to make a postal application and state their preference for alternative seating.
Additionally ST/LMTB Holders who wish to purchase other than their usual seat can do so on Thursday 5 September from 9am until 5pm, by telephoning the MUFC Ticket Line or alternatively by making an IMMEDIATE postal application enclosing letter of application, relevant voucher (duly completed), first class sae, open cheque (made payable to MUFC) or credit/debit card details (please note, an administration fee of 3% per transaction is charged).
Please ensure the incoming envelope is clearly marked “EUROPEAN”.
SALES TO MEMBERS:
Members are requested to make an IMMEDIATE postal application enclosing a match ticket order form, payment and sae. Please clearly indicate whether the application is for one or both games or alternatively by making an on-line booking.
Usual League Match prices apply. Please note the Junior Ticket scheme will be in operation for this game, seats are situated in the East Lower section of the stadium priced £9.50.
IN THE EVENT OF TICKETS REMAINING A FURTHER ANNOUNCEMENT REGARDING SALES WILL BE MADE ON FRIDAY 6 SEPTEMBER.