Well their booking system seems to suggest a very sparse 6-aircraft operation. I can only assume that it's either incomplete, or that some flights are being sold through other tour operators.
Mon LGW-CFU 0500 1010 VIK111 CFU-LGW 1110 1230 VIK112
Mon LGW-SSH 1355 2120 VIK113 SSH-LGW 2220 0155 VIK114
Mon LGW-DLM 1400 2010 VIK313 DLM-LGW 2110 2335 VIK314
Mon LGW-BJV 1735 2335 VIK315 BJV-LGW 0035 0245 VIK316
Tue LGW-CHQ 0500 1045 VIK325 CHQ-LGW 1145 1340 VIK326
Tue LGW-HER 0500 1055 VIK121 HER-LGW 1155 1400 VIK122
Tue LGW-TFS 0500 0915 VIK121 TFS-LGW 1005 1415 VIK122
Tue LGW-SSH 1515 2240 VIK123 SSH-LGW 2340 0315 VIK124
Wed LGW-RHO 0500 1055 VIK131 RHO-LGW 1145 1350 VIK132
Wed LGW-PFO 0700 1330 VIK333 PFO-LGW 1430 1715 VIK334
Thu LGW-ACE 0500 0905 VIK343 ACE-LGW 1005 1410 VIK344
Thu LGW-SSH 1430 2155 VIK143 SSH-LGW 2255 0230 VIK144
Fri LGW-HRG 1000 1730 VIK353 HRG-LGW 1830 2210 VIK354
Fri LGW-TFS 1300 1715 VIK900 TFS-LGW 1815 2230 VIK901
Fri LGW-DLM 1730 2340 VIK153 DLM-LGW 0040 0305 VIK154
Sat LGW-EFL 0500 1025 VIK363 EFL-LGW 1140 1305 VIK364
Sat LGW-KLX 0600 1135 VIK161 KLX-LGW 1235 1415 VIK162
Sat LGW-SSH 1430 2155 VIK365 SSH-LGW 2255 0230 VIK366
Sat LGW-KGS 1530 2125 VIK163 KGS-LGW 2225 0030 VIK164
Sun LGW-ZTH 0500 1025 VIK373 ZTH-LGW 1125 1255 VIK374
Sun LGW-SSH 1350 2115 VIK173 SSH-LGW 2215 0150 VIK174
Sun LGW-PFO 1400 2030 VIK375 PFO-LGW 2130 0015 VIK376
Mon MAN-CFU 0615 1140 VIK415 CFU-MAN 1240 1345 VIK416
Mon MAN-DLM 1500 2115 VIK417 DLM-MAN 2215 0050 VIK418
Tue MAN-TFS 0500 0930 VIK425 TFS-MAN 1030 1500 VIK426
Tue MAN-HER 0500 1100 VIK223 HER-MAN 1200 1415 VIK224
Tue MAN-SSH 1515 2240 VIK225 SSH-MAN 2340 0325 VIK226
Wed MAN-RHO 0500 1110 VIK435 RHO-MAN 1210 1430 VIK436
Wed MAN-KGS 0500 1110 VIK233 KGS-MAN 1210 1430 VIK234
Wed MAN-PFO 1600 2250 VIK235 PFO-MAN 2350 0255 VIK236
Thu MAN-ACE 0500 0910 VIK445 ACE-MAN 1110 1410 VIK446
Thu MAN-SSH 1100 1825 VIK243 SSH-MAN 1925 2310 VIK244
Fri MAN-JSI 0700 1240 VIK455 JSI-MAN 1330 1645 VIK456
Fri MAN-HRG 1100 1845 VIK253 HRG-MAN 1945 2345 VIK254
Fri MAN-TFS 1315 1730 VIK902 TFS-MAN 1830 2245 VIK903
Fri MAN-DLM 1800 0020 VIK457 DLM-MAN 0120 0400 VIK458
Sat MAN-EFL 0500 1040 VIK263 EFL-MAN 1140 1325 VIK264
Sat MAN-KLX 0600 1150 VIK465 KLX-MAN 1250 1450 VIK466
Sat MAN-SSH 1435 2200 VIK265 SSH-MAN 2300 0245 VIK266
Sat MAN-KGS 1600 2210 VIK467 KGS-MAN 2310 0130 VIK468
Sun MAN-ZTH 0500 1040 VIK273 ZTH-MAN 1140 1330 VIK274
Sun MAN-PFO 0800 1430 VIK475 PFO-MAN 1520 1815 VIK476
Having said that, take out the TFS flights (notice the Tuesday flight from Gatwick seems to have the same flight number as the HER flight...) and it works out at 5 aircraft, but is still rather thin on some days.