The coupon on those RPS is 13.5%. The negative cash flow of the airport is roughly the coupon on those debts. Indeed if you don’t include the coupon on the RPS as an interest cost then
If we were to restructure the RPS as equity (which is fair enough as it is subordinated and stapled to the equity) then
Sydney Airport will still be insolvent with a large fall traffic volumes but a few years of flat to slightly declining volumes is probably supportable provided that there are no short term maturities and the coupons on the subordinated debt get halted. (The listed entity - Macquarie Airports - would still get smashed under these circumstances - but the bond insurers would be OK.)
It also remains true that the debt of Sydney Airport has gone up more or less every year since the Macquarie takeover - and the distributions have been funded by debt.
That can't continue with (a) bad credit markets or (b) falling or even stable traffic.