It looks like the extra aircraft is coming from Boeing.
Flying at the minute Fri - Sat -Sun and Mon and likely to be standby tue wed and thu to cover maintenance.
Friday - LS1241 BHX - HER 0855/1300 1350/1815
Saturday - reshuffle of a few flights to add a rotation to RHO and CFU.
LS1283 BHX - RHO 1235/1645 1745/2210
LS1213 BHX - CFU 1535/1905 2005/2335
Sunday - LS1263 BHX - MAH 0710/0945 1030/1305
LS1283/4 BHX - RHO 1305/1710 1800/2335
Monday LS1273 BHX - ZTH 1015/1355 1440/1830
All time in Zulu