Fill-in-the-Blanks Kwiz Changement de programme

Question

I’m posting here because fill-in-the-blanks Kwizzes don’t have Q&A. 
The last answer is:  Dans ce cas, je vais appeler Bruno avant qu'il réserve le restaurant, et je n'ai plus qu'à espérer qu'il ait du temps plus tard ! 
I’m wondering why the "avoir" in "espérer qu’il ait du temps" is subjunctive, as espérer is usually followed by an indicative. Is it triggered by "je n’ai plus qu’à"? Or because it’s only possible that he’ll have time?
 
 (Also, the Kwiz is headed Subjonctif présent and passé but all the answers are present tense) 
 
 https://progress.lawlessfrench.com/my-languages/french/tests/take/2770864?isRetake=1

Cécile Janty-Davies · Accepted Answer

Bonjour Anne,
The use of the subjunctive after 'espérer que' always depends on the degree of doubt and uncertainty in what you hope to happen. It is used mainly with negative and interrogative constructions.
You are correct that the use of the ' on n'a plus qu'à ' ( to have nothing else to do but ) shifts this sentence to a negative construction, which carries a nuance of resignation or doubt, which triggers the subjunctive in the subordinate clause.
As to your last comment, there is one subjonctif passé :
Amélie est si heureuse que tu ___ d'être sa demoiselle d'honneur = Amélie is so happy that you agreed to be her bridesmaid.
Bonne Continuation!