| 84-11 | 604-1 | Possible damage of wing structure with water ballast bags installed. Revision of flight manual. All S/N | | German | English |
| 86-220 | 604-2 | Rudder-yoke Replacement of the yoke. All S/N | Before 31/3/1987 | German | English |
| 87-83 | 604-3 | Replacement of "DN" control cables by "LN" cable. All S/N | Before 31/7/1987 then every 500 hours | German | English |
| 604-4 | Tow releases: Optional use of model E85 instead of E72/E75. All S/N | | German | English |
| 93-001 | 604-5 | L’Hotellier ball and swivel joints, Installation of safety pin. All S/N | Before 31/3/1993 | German | English |
| 96-141 | 604-6 | Control surface weight and static balance. All S/N | Before 31/3/1996 | German | English |
| 96-135 | 604-7 | Inspection of glass fiber laminate on spar stub fitting, All S/N | Annually | German | English |
| 604-8 | Installation of Mode-S-Transponder and Transponder Antennas | | German | English |
| 604-9 | Inspection of glass fiber laminate on spar stub fitting, All S/N (replaces TN 604-7) | Annually | | |
| 604-10 | Spar stub fitting replacement, standardisation of fittings | | German | English |
| EASA AD 2011-213 | 604-11 | Inspection / replacement of elevator control rod in vertical fin | 30 days, Before 31/12/2012 | German | English |
| 604-11 | Authorised service facilities for TN 604-11 | | German | |
| 604-12 | Increase of the operating time | Before 3000 hours | German | English |
| 604-13 | Continuous Canopy with pop-up mechanism | | German | English |
| 604-14 | Installation of backrest with integrated headrest | | German | English |
