When the price hits a given level, program participants can purchase additional allowances beyond the annual cap. (eia.gov)
Please refer to individual carriers for potential baggage charges and more information should you require additional allowance. (staralliance.com)
This is similar to the technique described by Kaplan et al. (1997, 1998) but with additional allowance for non-stationarity of the data (Parker et al, 1995). (ipcc.ch)